Ramanujan’s Number

1729 is called Ramanujan’s number. This number became famous through a conversation between two great mathematicians – Srinivasa Ramanujan and Godfrey Harold Hardy. The English mathematician G.H. Hardy recalled:

“I remember once going to see him when he was ill at Putney. I had ridden in taxi cab number 1729 and remarked that the number seemed to me rather a dull one, and that I hoped it was not an unfavorable omen. “No,” he replied, “It is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways.”

The number 1729 can be expressed as the sum of the cubes of 1 and 12, and also as the sum of the cubes of 9 and 10.

1729 = 1³ + 12³ = 9³ + 10³