**997**is a prime number. It is the largest three-digit prime.

**997**is the smallest prime of the form 10

^{p}-

*p*, where

*p*is prime (3).

**997**is the smallest prime whose sum of digits (25) is an odd composite number.

**997**is the smallest prime

*p*such that the sum of the digits of

*p*(9 + 9 + 7 = 25) is not prime, but the sum of the squares of the digits is prime (9

^{2}+ 9

^{2}+ 7

^{2}= 211).

**997**is the smallest prime

*p*such that the sum of the digits of

*p*(9 + 9 + 7 = 25) is not prime, but the sum of the cubes of the digits is prime (9

^{3}+ 9

^{3}+ 7

^{3}= 1801).

**997**has a representation as a sum of two squares:

**997**= 6

^{2}+ 31

^{2}.

**997**is the hypotenuse of a primitive Pythagorean triple:

**997**

^{2}= 372

^{2}+ 925

^{2}.

Sourcea: Number Gossip and Prime Curios!

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