- During one visit to Ramanujan in the hospital at Putney, Hardy mentioned that the number of the taxi cab that had brought him was 1729, which, as numbers go, Hardy thought was "rather a dull one", and that this was a bad omen. At this, Ramanujan perked up, and said "No, it is a very interesting number; it is the smallest number expressible as a sum of two cubes in two different ways."

- During one visit to Ramanujan in the hospital at Putney, Hardy mentioned that the number of the taxi cab that had brought him was 1729, which, as numbers go, Hardy thought was "rather a dull one", and that this was a bad omen. At this, Ramanujan perked up, and said "No, it is a very interesting number; it is the smallest number expressible as a sum of two cubes in two different ways."

The issue of classifying numbers as "dull" and "interesting" leads to an interesting paradox (strictly speaking, an antinomy). In a classification of numbers as to whether they had interesting properties or not, there would be a smallest number with no interesting properties (for instance, 38 could be a candidate). This in itself would be an interesting property of the number, making it interesting, thus excluding it from the list. Closely related paradoxes/antinomies are the Berry paradox and the Liar paradox.

This article is about the number 1729. For the year AD 1729, see 1729.

- Mathworld: Hardy-Ramanujan number
- Mathworld: Taxicab number