An emirp is a prime numberMathworldPlanetmath that in a given base b reads like a different prime number backwards. The plural of emirp is emirps, but semirp is occasionally used by amateurs.

For example, in base 10, the number 37 read backwards is 73, both of these are prime. The backwards number must be different. A006567 of Sloaneā€™s OEIS lists the first fifty base 10 emirps.

A palindromic primeMathworldPlanetmath is not an emirp, since it reads the same number both ways. Thus, in binary, Mersenne primesMathworldPlanetmath can not be emirps.

Title emirp
Canonical name Emirp
Date of creation 2013-03-22 17:06:54
Last modified on 2013-03-22 17:06:54
Owner PrimeFan (13766)
Last modified by PrimeFan (13766)
Numerical id 4
Author PrimeFan (13766)
Entry type Definition
Classification msc 11A41
Classification msc 11A63
Defines semirp