**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!