1729

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Summary

Names

This number is called the Hardy-Ramanujan number after a conversation between Hardy and Ramanujan where Ramanujan observed that it is the smallest number expressible as the sum of two cubes in two distinct ways: $\!1729=10^{3}+9^{2}3=12^{3}+1^{3}$.

Factorization

$\!1729=7\cdot 13\cdot 19$

Properties and families

Property or family	Parameter values	First few numbers
Carmichael number	third among them	561, 1105, 1729, ...
Poulet number ([[Fermat pseudoprime to base 2)	sixth among them	341, 561, 645, 1105, 1387, 1729, 1905, 2047