# Find next number

Find the next number from the following

19 => 730

28 => 520

37 => 370

45 => 189

63 => ?


The number is

243

For the calculation rule

consider the number on the left consisting of two digits $AB$. The number on the right is $(A \times A + B \times B - A \times B) \times (A + B)$

• That expression is simpler to write as $A^3+B^3$. – f'' Jul 21 '15 at 10:22
• Good catch, I should keep a paper at hand for these kind of riddles. :-) – Moghwyn Jul 21 '15 at 10:27
• @Moghwyn Reminds me about Counting the Legs and dividing by 4 Joke to determine the number of Cows in a farm. – kanchirk Jul 21 '15 at 14:28
• @f'': Just for clarity -- the entire expression should be $(A^3 + B^3) \times (A + B)$? – GentlePurpleRain Jul 21 '15 at 15:52
• @GentlePurpleRain No. Check the math with both formulas. – Joe M Jul 21 '15 at 16:04