7

7 is the integer succeeding 6 and preceding 8.

properties
7 is an odd prime.

7 is the 2nd Mersenne prime.

7 is the 1st Woodall prime.

7 is the largest known n such that n! + 1 is a square number.

There are 7 continents on earth.

7 is said to be a lucky number.

A 7 sided polygon is called a heptagon.