Euler Phi Function/Examples/16

Example of Use of Euler $\phi$ Function
The value of the Euler $\phi$ function for the integer $16$ is $8$.

Proof
From the corollary to Euler Phi Function of Prime Power:
 * $\phi \left({2^k}\right) = 2^{k-1}$

Thus:
 * $\phi \left({16}\right) = \phi \left({2^4}\right) = 2^3 = 8$