Why is 1729 known as Ramanujan's number?
The number 1729 is known as the Hardy-Ramanujan number after Cambridge Professor GH Hardy visited Indian mathematician Srinivasa Ramanujan at a hospital. As Hardy called his taxi number 1729 "dull", Ramanujan exclaimed it was the "smallest number expressible as the sum of two cubes in two different ways," as the sum of cubes of 1, 12 and also 10, 9.