5

This number is a prime.

Just showing those entries submitted by 'De Geest': (Click here to show all)

5 is the smallest first member of a twin primes pair (a, b) such that (a + b) +/- 1 is a second twin primes pair (c, d). [De Geest]

F_n = 2^(2^n) + 1 are semiprimes for n = 5, 6, 7, and 8. [De Geest and Honaker]