Math Fun Library 


Question : 
Is 1729 Unlucky ? 
Answer : 
1729 is the only known number that is sum of two cubes in two different ways. 
10^{3} + 9^{3} = 1729; 12^{3} + 1^{3}
= 1729 
This is popularly known as Ramanujan's number. The great Indian Mathematician, was sick in the hospital, Prof. Hardy,
his tutor paid him a visit. Prof. Hardy told Ramanujan that he rode a taxi to the hospital with a very unlucky number,
1729.

Masahiko Fujiwara showed that 1729 is one of four natural numbers
(the others are 81 and 1458 and the trivial case 1) which, when its digits are added together,
produces a sum which, when multiplied by its reversal, yields the original number,

1 + 7 + 2 + 9 = 19
19 x 91 = 1729

