Euler Phi Function/Examples/16

Example
The value of the Euler $\phi$ function for the number $16$ is determined as follows:

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

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