257

This number is a prime.

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The only prime of the form a^a + b^b where a and b are one-digit non-prime integers. [Loungrides]

The only prime-digit prime whose absolute value of the differences between any two of its digits are also prime. [Loungrides]

The smallest prime-digit prime with distinct digits that is the sum of three prime-digit primes, i.e., (7+23+227). Note that the concatenation in order of these primes, i.e., 723227 is also prime. [Loungrides]