Euler Phi Function of 111

Example of Euler $\phi$ Function of Non-Square Semiprime

$\phi \left({111}\right) = 72$

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

Proof

We have that:

$111 = 3 \times 37$

Thus:

\(\ds \phi \left({111}\right)\)

\(=\)

\(\ds \left({3 - 1}\right) \left({37 - 1}\right)\)

Euler $\phi$ Function of Non-Square Semiprime

\(\ds \)

\(=\)

\(\ds 2 \times 36\)

\(\ds \)

\(=\)

\(\ds 72\)

$\blacksquare$