56

This number is a composite.

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Sigma(56) equals the first prime of the form 6n - 1 factorial, 5!. [Noll]

2^{56 - 1} - 56 + 1 is prime. [Noll]

The number of products of distinct primes less than or equal to 11 (the only palindromic prime with an even number of digits) which are congruent to -1 mod 11 is 56. [Noll]