There's an interesting way of looking at this, which is that a prime is a number, p, such that when p divides into a product, it divides into one of the factors

There's an interesting way of looking at this, which is that a prime is a number, p, such that when p divides into a product, it divides into one of the factors of the product. Then 1 divides into the empty product, but not into any of its factors.