I've heard stories about why the number $1$ is neither a prime number nor a composite number, even on in the middle of this awesome math page.
Just scroll down to the middle to read about it. It's a bit short.
Anyway, let's cut to the chase. How come $1$ isn't a prime number or even a composite number? I want to know from your great-heard-of answers! At least I know that a prime number has only two factors, $1$ and itself. So, why isn't this the same for $1$? It has a factor of $1$, which is also itself, $1$. I want to hear about this, too.