1556

This number is a composite.

This number, whose reversal is prime, is the sum of the squares of the first 9 primes: 1556 = 2^2 * 389 = 2^2 + 3^2 + 5^2 + 7^2 + 11^2 + 13^2 + 17^2 + 19^2 + 23^2. [Post]