1111211111
This number is a prime.
1
1 1
1 2 1
1 1 1 1
The smallest triangle-congruent prime.
The near-repunit prime 1111211111 is the largest prime factor of 1234567890987654321. [Poo Sung]
Printed from the PrimePages <t5k.org> © G. L. Honaker and Chris K. Caldwell