This number is a prime.
The first three Fermat primes (3,5,17) form a prime when concatenated forwards or backwards. They also form primes when concatenated forwards or backwards with a zero inserted between each number. [Vouzaxakis and Hartley]
(There is one curio for this number that has not yet been approved by an editor.)
Printed from the PrimePages <t5k.org> © G. L. Honaker and Chris K. Caldwell