
Curios:
Curios Search:
Participate: 
281683 is the smallest prime such that if F(p) = 2*p^21, then F(281683), F(F(281683)), F(F(F(281683))), and F(F(F(F(281683)))) are also primes. [Opao]
Prime Curios! © 20002018 (all rights
reserved)
