11

This number is a prime.

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11=1+2+8 and the only known values of n for which (p(n)^p(n)-1)/(p(n)-1) is prime are n=1,2,8, and 11. [Rupinski]

The smallest prime p such that 6p ± 1 do not form a twin prime pair. [Rupinski]

There are exactly 11 positive odd integers N that cannot be expressed as the sum of two coprime composite integers, both of which are less than N. [Rupinski]