This number is a prime.

+ The smallest (the only known) Pell number that is an emirp. Note that the sum of its digits is also emirp. [Loungrides]

+ Summing the reciprocals of the semiprimes of semiprime index first gives a value greater than 1, only after this emirp number of terms. [Merickel]

Printed from the PrimePages <t5k.org> © G. L. Honaker and Chris K. Caldwell