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.

Filter by
Sorted by
Tagged with
25
votes
1answer
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 ...
4
votes
1answer
174 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 * ...
2
votes
2answers
210 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?
2
votes
1answer
214 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, ...
1
vote
1answer
152 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 ...
2
votes
2answers
392 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 ...
0
votes
1answer
255 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 ...
15
votes
2answers
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 ...
5
votes
1answer
137 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 ...
7
votes
2answers
303 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 ...
5
votes
1answer
260 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 ...
14
votes
2answers
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" ...
2
votes
1answer
170 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. ...
12
votes
2answers
994 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 ...
16
votes
1answer
793 views

What number goes in the ?? box?

A simple pattern puzzle What is the number in the ?? box? Why? No programming please.
5
votes
2answers
209 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"... ...
0
votes
1answer
77 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 ...
8
votes
3answers
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 ...
3
votes
2answers
153 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 ...
9
votes
1answer
457 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?
3
votes
1answer
143 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 ...
7
votes
2answers
471 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 $x$ ...
5
votes
2answers
572 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 ...
3
votes
1answer
191 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 ...
0
votes
1answer
685 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 ...
11
votes
2answers
513 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 ...
51
votes
1answer
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, ...
12
votes
1answer
874 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 ...
2
votes
1answer
107 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 ...
-2
votes
1answer
130 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.&...
4
votes
2answers
225 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.
17
votes
2answers
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 ...
12
votes
1answer
390 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 ...
10
votes
0answers
420 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 ...
16
votes
1answer
983 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}}...
6
votes
9answers
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 ...
5
votes
1answer
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 ...
5
votes
2answers
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 ...
6
votes
4answers
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. ...
1
vote
1answer
112 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
4
votes
1answer
164 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
10
votes
0answers
431 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, ...
18
votes
1answer
1k views

What node does 11 point to?

If we included 11 in the diagram below, which node would it connect to? Hint 1
2
votes
1answer
94 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 ...
6
votes
1answer
566 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: ...
8
votes
2answers
596 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, ...
6
votes
1answer
184 views

Numbers with vowels used twice

This question is linked to Numbers in series If you write out the numbers the British way (using "and") What is the smallest number that has all the vowels used exactly twice. What is the ...
6
votes
1answer
165 views

Find the location of the royal artifacts

London, 13:20 While media and experts are still baffled on how Inspector Arbor caught Norman Erdmann (can you solve it? See here) Arbor himself has no time to rest. Police has already questioned ...
6
votes
1answer
442 views

Mathematical Coincidence

A friend came up to me today with a deck of cards, and put these 6 into a group: 2 3 5 7 J K The other 7 values went into another group: A 4 6 8 9 10 Q He then challenged me to find the reason ...
8
votes
3answers
1k views

What comes next in this sequence, and why?

I'm having the hardest time with this sequence puzzle. The mobile game I play (which asked me the question) doesn't provide answers or explanations for incorrect answers, and I'm searching online so I ...