19

This number is a prime.

Single Curio View:   (Seek other curios for this number)
19 = sigma(1*9) + phi(1*9). It is the only known prime with this property. [Firoozbakht]

Submitted: 2010-06-28 04:54:08;   Last Modified: 2020-07-04 01:25:21.
Printed from the PrimePages <t5k.org> © G. L. Honaker and Chris K. Caldwell