1.NounA prime number that becomes a different prime when its decimal digits (or digits in some specified other base) are reversed."The sequence of emirps begins: 13, 17, 31, 37, 71, 73, 79, 97, 107, ...; The first few emirps in base 12 (using the convention T for ten and E for eleven) are: 15, 51, 57, 5E, 75, E5, 107, ..."