Euler Phi Function of 666 equals Product of Digits

Theorem
The number $666$ has the following interesting property:


 * $\phi \left({666}\right) = 6 \times 6 \times 6$

where $\phi$ denotes the Euler $\phi$ function.

Proof
From Euler Phi Function of Integer:
 * $\displaystyle \phi \left({n}\right) = n \prod_{p \mathop \backslash n} \left({1 - \frac 1 p}\right)$

where $p \mathop \backslash n$ denotes the primes which divide $n$.

We have that:
 * $666 = 2 \times 3^2 \times 37$

Thus: