91812151
This number is a prime.
The only emirp concatenated from the double-digit composite numbers ending with 1, i.e., 21, 51, 81, 91. [Loungrides]
Printed from the PrimePages <t5k.org> © G. L. Honaker and Chris K. Caldwell
This number is a prime.
The only emirp concatenated from the double-digit composite numbers ending with 1, i.e., 21, 51, 81, 91. [Loungrides]