Number 1729 and Taxi Cabs

About this video

The story behind number 1729.

The number 1729 is famous amongst mathematicians, but why? Dr James Grime and Professor Roger Bowley reveal the much-loved anecdote behind the number.

In the early twentieth century, when British mathematician Godfrey Harold Hardy became a mentor to Indian mathematician, Srinivasa Ramanujan. When Ramanujan became ill, Hardy visited him in hospital and happened to remark on the number of the taxi that had brought him there.

Contrary to Hardy's claims that the number 1729 was uninteresting, Ramanujan pointed out it was the smallest number that could be represented in two ways as a sum of two cubes. The number later became known as the 'Hardy-Ramanujan number'.  

This film forms part of the Numberphile series by filmmaker Brady Haran.