This number is a composite.
512 = 2^9. Both 2^9 +/- 9^2 are prime. This is the smallest number of the form 2^n such that both 2^n +/- n^2 are prime. [Astle]
(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