A

David

Darling

emirp

An emirp is a prime number that becomes a different prime number when its digits are reversed ("emirp" is "prime" spelled backwards). The first twenty emirps are 13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149, 157, 167, 179, 199, 311, 337, 347, 359, and 389. Compare with a palindromic prime (see palindromic number), which gives the same prime when reversed.