Math Wiki

11 is the integer the proceeds 10 and preceeds 12.

This is the first two-digit palindrome number and the fifth prime number.

A number is divisible by 11 if the alternating series of even place and odd placed numbers are divisible by 11. 

11 is the smallest prime p such that 2^p-1 is composite. 2^11-1 = 2047 = 23*89. 

11 is a Wagstaff prime.