Sum of Reciprocals of Powers as Euler Product

Theorem
Let $\zeta$ be the Riemann zeta function.

Let $s\in \C$ be a complex number with real part $\sigma > 1$.

Then:
 * $\displaystyle \map \zeta s = \prod_p \frac 1 {1 - p^{-s} }$

where the infinite product runs over the prime numbers.