15555...55551 (33-digits)
This number is a prime.
155 5555555555 5555555555 5555555551
The digital sum of this prime is 157, another prime (whose digit sum in turn is yet another prime: 13). [Trotter]
(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