So we know what prime numbers are, and we have some idea of how they're important.  (Remember, they're the building blocks of all other positive whole numbers.)  But why are mathematicians so fascinated with them?  Isn't it maybe bordering on an unhealthy obsession?  I mean, there are so many other numbers out there; why focus so much energy on only a tiny fraction of them?

Well, check out this article about Ulam's Spiral.  It's a perfect example of how prime numbers are at the same time incredibly amazing and frustratingly elusive.