Don't remember much of a syntax in C++..I can think only in VBA. But the logic I can think of for the "emirp" part is: First: Convert the Number to String. Probably like this: string B = (string) A. Second: Reverse the String using some code (probably the one here: http://uw714doc.sco.com/en/SDK_c++/_Reverse.html) Third: Convert the reverse string back to number. (how?) and then test for prime or no prime. Other guruz might know better. Good luck.