135
This number is a composite.
The two prime factors of 135 are 3 and 5. Note that, starting with 3, the sum of 5 consecutively squared integers equals 135. [Cramer]
Both 1!+3!+5! and 1!!+3!!+5!! are primes. [Jevtic]
(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