13

Thirteen (13) is a positive integer one more than 12 and one less than 14.

Properties
13 is the sixth prime number (between 11 and 17). It is a member of a twin prime pair with 11.

13 is a Mersenne prime exponent, producing 8191.

13 is the seventh Fibonacci number, between 8 and 21.

Despite widely being considered unlucky, it is a lucky number (between 9 and 15).