Let me start by saying that prime numbers have absolutely no practical significance in the working of the universe to my knowledge. In a world filled with everything arbitrary (language, art, law, money etc. are all artificial human constructs), I am fascinated by the idea that prime numbers (and some other very basic mathematical concepts) aren't created by anyone or anything, they just ARE! They are the same no matter what culture, country or galaxy you are from, and no matter what number system you use (eg. binary, hexidecimal). They existed before we did. Why ARE they?