What does the number 31 signify?

31 is a Prime number.

= 2 + 2 + 2 + 2 + 2

The sum of five powers of 2.

= 5 + 5 + 5

The sum of three powers of 5.

= 2 - 1

A Mersenne prime.

There are 31 letters in the Cyrillic (Russian) alphabet.

Thirty-one is a betting game played with cards.

In French the expression trente et un means someone who is well dressed.