This number is a prime.

+ The concatenation of the five known Fermat primes 3, 5, 17, 257, and 65537. Concatenate them backwards, 655372571753, and it remains prime. [Rivera]

(There is one curio for this number that has not yet been approved by an editor.)

Printed from the PrimePages <primes.utm.edu> © G. L. Honaker and Chris K. Caldwell