What is the significance of '1729', the Hardy-Ramanujan number?
British mathematician GH Hardy once took a cab numbered '1729' to visit Indian mathematician Srinivasa Ramanujan in the hospital. While Hardy found it to be an ordinary number, Ramanujan said it's the smallest number that can be expressed as sum of two cubes in two ways. '1729' is sum of cubes of one and 12 and of nine and 10.