Questions tagged [number-property]

Puzzles that use number properties such as even and odd, multiples of numbers, part of a well-known sequence (i.e. Fibonacci) or theorem (Pythagorean relations) or others in part of the method to solve the question.

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I wonder what that would be

This is my own puzzle. Consider the following Alice begins march for peace in East Bengal along with Gandhi Bentley celebrated the first Bahia Independence Day Catherine saw the starting of the Great ...
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1 vote
0 answers
61 views

Number message with cryptic key: "3656 8797 1232 6484..."

A cryptic message received: The start and end win race Second and last equal key First and third define it 3656 8797 1232 6484 0959 6585 3878 9090 5474 2141 8999 5484 1838 5676 9373 4262 What does ...
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8 votes
7 answers
4k views

How can four be the half of five? [closed]

I came across this enigmatic one-liner: How can four be half of five? Can you figure it out?
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25 votes
1 answer
2k views

What is a Chess Number™?

This is in the spirit of the What is a Word/Phrase™ series started by JLee with Number version puzzles. If a number conforms to a special rule, I call it a Chess Number™. Use the following examples ...
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  • 1,954
4 votes
1 answer
187 views

Fractions and Fractional Numbers

Using fractions and fractional numbers of the digits $1$ to $10$ and only the mathematical operations of addition, subtraction, multiplication, and division, including parenthesis (e.g. $1 + 2 - (3 * ...
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2 votes
2 answers
213 views

Consecutive integers which have digital sums that are not relatively prime

What are ten smallest natural numbers n, such that n and n+1 have digital sums which are not relatively prime?
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2 votes
1 answer
223 views

What number comes next in this evenly doubled sequence?

I've been playing around with sequences lately and found a pretty evenly doubled sequence of single digit numbers: 1, 12, 30, 64, 65, 156, 175, 368, 369, 371, 752, 753, 1524, 1525, 3060, 3073, 6168, ...
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1 vote
1 answer
160 views

An oddly formed sequence?

I've been playing around with sequences lately and came across one that was rather, odd. $101$, $123$, $147$, $189$, $191$, $213$, $217$, $279$, $...$ Hints Let $N_i = 101$... Can you determine the ...
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2 votes
2 answers
397 views

A dance between numbers

Given the following equation: $$\Delta = \Biggl(\frac{t \mod 6}{(t \mod r) + 1}\Biggr)^2$$ Find the relationship between $t$ and $r$, along with the properties of each, that ensures $\Delta = 9$. For ...
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0 votes
1 answer
279 views

The maze of everlasting flowers

You were recently caught trespassing on the queen's hunting grounds. The punishment for this crime is a miserable experience the locals call the maze of everlasting flowers: The full resolution of ...
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15 votes
2 answers
1k views

Scrabble with prime numbers!

How to Play Overall, gameplay is very similar to typical Scrabble; however, unlike typical Scrabble, you'll be using digits instead of letters (we'll cover your tile bag later). The objective is to ...
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5 votes
1 answer
144 views

The digits of the cube of a 3-digit number X

The digits of the cube of a certain 3-digit number X are, from left to right, the square of a 2-digit number, followed by the square of another 2-digit number, followed by one digit. (Everything is ...
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7 votes
2 answers
310 views

Integers containing all ten digits

It is known that most positive integers contain at least one copy of each of the ten digits. What is the largest n such that at most 50% of the integers in the set [1,2,3,...,n] contain at least one ...
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5 votes
1 answer
263 views

Mapping days as a 4 digit number! [closed]

I have a puzzle that includes mapping days as a 4 digit number. Sunday: 6137 Monday: 6240 Tuesday: 7358 Wednesday: 9497 Thursday: 85?? The first digit is just the number of characters and the second ...
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11 votes
1 answer
853 views

The largest Saturday number

No weekend love yet shown, therefore I will fix that. A Saturday number is a number in which for all $1 \le i \le l$, where $l$ is the length of the number, the first $l$ digits (from the left) divide ...
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14 votes
2 answers
2k views

Largest number with no repeating digit pairs

What is the largest whole number that you can form, such that no pair of consecutive digits occurs more than once? For example you can have 34543, but you cannot have 34534 as the pair "34" ...
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2 votes
1 answer
175 views

Adding up divisors of integers

Alice and Bob play a game, taking turns. Alice starts and writes an integer between 1 to 10 on a blackboard. Then Bob adds any integer between 1 to 10 to this number and writes it on the blackboard. ...
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12 votes
2 answers
1k views

Making a 10 digit number divisible by 3

Alice and Bob play the following game, taking turns. Alice starts and writes a single digit from 0 to 9 at the blackboard. At every turn, each player adds a single digit at the right of the current ...
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16 votes
1 answer
810 views

What number goes in the ?? box?

A simple pattern puzzle What is the number in the ?? box? Why? No programming please.
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5 votes
2 answers
217 views

Odd numbers to Even numbers

Remember the old puzzle? "Can you take just one letter out of an odd number and make it even?" Note the clever wording. It just says make it even; not "make it an even number"... ...
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0 votes
1 answer
88 views

Largest 5-digit palindrome in base 16, where each digit appears at most twice

What is the largest number $ x $ such that $ x_{16}, $ i.e. $ x $ in base 16, is a 5-digit long palindrome, where each digit appears at most twice? A palindrome is a number that reads the same forward ...
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  • 111
8 votes
3 answers
2k views

When should this question be answered?

If you hover your mouse over the time marked in the right-bottom corner of this post, then you will see a string showing the exact time that I post this question, which reads ...
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  • 6,967
3 votes
2 answers
159 views

What is the house number in nolteight street

Alice moved to nolteight street. Bob meets her after her move, and he knows that the smallest house number in nolteight street is 8, and the highest number is 100. But he does not know Alice's house ...
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9 votes
1 answer
460 views

Consecutive integers with digit sum divisible by 19

What is the smallest positive integer N, such that the digit sum of N and N+1 are both divisible by 19?
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3 votes
1 answer
144 views

A function. Really?

If you give me a 5, I give you a 21. If you give me a 6, I give you a 2. If you give me a 7, I give you a 12. If you give me a 10, I give you a 101. What am I processing to get the result? Hint 1 ...
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  • 1,149
7 votes
2 answers
491 views

When do decimal-coded binary numbers XOR to zero?

Background definition: XOR on numbers Given two non-negative integers $x$ and $y$, let $x\oplus y$ denote the bitwise exclusive or (XOR) of the numbers $x$ and $y$. This is the result of writing $x$ ...
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  • 549
5 votes
2 answers
574 views

Sort 10 clock numbers

An electronic clock shows hours and minutes: from 00:00 to 23:59. Sort the numbers 0, 1, ..., 9 according to the time of their presence on the clock board during the 24-hours. Edit For example, for ...
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  • 1,691
3 votes
1 answer
195 views

What is so unique about these four numbers?

These four numbers look like four ordinary numbers. But I found something unique about these four that I may be only true for one other set of numbers-- unless you raise the bar-may be. So what is ...
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  • 38.8k
0 votes
1 answer
690 views

100 lightbulbs in a room [duplicate]

There are 100 lightbulbs in a room, each with it’s own switch in the off position (all lightbulbs work and start off, no funny business). There are also 100 people numbered from 1 to 100 standing ...
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11 votes
2 answers
519 views

Welcome to the Acme Corporation - please find your floor number

Welcome to the Acme Corporation. The Acme Corporation is the greatest company in the world, and it should be your utmost honor and privilege to be employed as an associate of the Corporation. The ...
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  • 147
51 votes
1 answer
3k views

After the funeral

The mood was sombre in the lawyer’s office. Eight members of the Picodie family gathered together to hear the reading of their recently deceased father’s will. Around the table sat Eli, Ron, Agnes, ...
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  • 96.8k
12 votes
1 answer
877 views

Lawbreaking by the numbers

Special Agent Benford has been stymied by a third unsolved case of miscreant creative accounting and will voluntarily retire from the Fraudulent Numbers Task Force. Benford’s ability to detect ...
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2 votes
1 answer
108 views

Numbers with a shared property

The following numbers share same property. What are the next two numbers with same shared property? What are the previous two with the same shared property? What is the largest three digit number with ...
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-2 votes
1 answer
131 views

How many pigeons are in the flock? [closed]

A crow reaches a flock of pigeons. the crow asks the pigeons' leader: "How many of you are there?" The pigeon replies: "We and we and a half of we and a fourth of we and you equal 100.&...
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4 votes
2 answers
233 views

The number game

There is a number, the second digit of which is smaller than the first digit by $4$, and if the number was divided by the digits' sum, the quotient would be $7$. What is this number.
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  • 1,149
17 votes
2 answers
2k views

What is the secret operator?

There is a secret operator $F$ that takes two whole numbers and outputs a new number. For example $$\begin{split}F(6,9) &= 15\\ F(66,11) &= 110 \\ F(86,18) &= 179\end{split}$$ Can you ...
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12 votes
1 answer
401 views

What is a Trinity Number™?

This is inspired by the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles, and the Number™ series. If a number conforms to a special rule, I call it a ...
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  • 10.1k
10 votes
0 answers
432 views

Dead By Daylight

This puzzle is a reference to a game, Dead By Daylight. Though you don't need a knowledge about the game. Consequently, there is no "video-games" tag. Story The Entity wants to have the ...
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  • 3,329
16 votes
1 answer
1k views

What is the Color Code™?

Inspired from Can you name the country code? and What is a Number™? series $ \begin{gather} % custom template - reuse if you may \def\S#1#2{\Space{#1}{21px}{#2px}}\def\P#1{\V{#1em}}\def\V#1{\S{#1}{9}}...
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  • 5,557
7 votes
9 answers
2k views

Multilanguage generalization of "What number is that? Asks Grandpa"

This is a multilingual generalized follow-on to "What number is that? Asks Grandpa", which I restate as: "What is the smallest positive English integer N, for which if you take its WORD anagram and ...
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  • 841
5 votes
1 answer
146 views

Follow the path of relation through the grid #6

There is a relation between rectilinear-adjacent squares such that there is a unique rectilinear path from the top-left corner of the grid down to the bottom-right corner of the grid. Each square can ...
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  • 2,212
5 votes
2 answers
227 views

Follow the path of relation through the grid #5

There is a relation between rectilinear-adjacent squares such that there is a unique rectilinear path from the top-left corner of the grid down to the bottom-right corner of the grid. Each square can ...
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  • 2,212
6 votes
4 answers
1k views

What is larger than largest, your intuitions are tarnished. (What am I?)

You might call me a number, but that would be a blunder. In class you may have been told otherwise, but I tell you now that those were all lies. I'm in the deck of the cards, as big as them come. ...
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  • 2,212
1 vote
1 answer
113 views

A simple matter of relations (What am I?)

Don't overthink it, just a little fun. Relations are part of graphs, of which I am one. What is my relation? Hint 1
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  • 2,212
4 votes
1 answer
165 views

Which node(s) does 0 connect with in this simple graph?

If we add 0 as a node to the graph below, which node(s) will it connect to? Hint 0 Hint 1 Hint 2
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  • 2,212
10 votes
0 answers
438 views

I'm a number with a special product, so name me when you think you've got it

In the blocks that come before, their special product tells us more. To guess my scheme you'll need calculation, but only little tests of recreation. Each block contains atoms strong as Thor, ...
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  • 2,212
18 votes
1 answer
1k views

What node does 11 point to?

If we included 11 in the diagram below, which node would it connect to? Hint 1
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  • 2,212
2 votes
1 answer
102 views

Pandigital Puzzle

Can you find the 10 digit number* which contains each of the digits 0-9* exactly once, and when divided by 9 the quotient is a perfect cube which has the digit 7 in it exactly twice*? *in its base 10 ...
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6 votes
1 answer
573 views

Who's that Simple Pokémon™?

For every alphabet (A to Z), there exists at most one corresponding Simple Pokémon™. As of Generation 8, it goes: ...
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  • 3,329
8 votes
2 answers
606 views

Which famous mathematical constant can be celebrated on these dates?

Which famous mathematical constant can be celebrated on these dates? April 11, 2020 April 12, 2021 April 12, 2022 April 12, 2023 April 11, 2024 April 12, 2025 April 12, 2026 April 12, 2027 April 11, ...
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