6408

This number is a composite.

6408, made from a nonprime number of nonprime digits, is the sum of the squares of the first 13 primes: 2^2 + 3^2 + 5^2 + 7^2 + 11^2 + 13^2 + 17^2 + 19^2 + 23^2 + 29^2 + 31^2 + 37^2 + 41^2 = 6408 = 2^3 * 3^2 * 89. [Post]