Numbers with Euler Phi Value of 72

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Example of Use of Euler $\phi$ Function

There are $17$ positive integers for which the value of the Euler $\phi$ function is $72$:

$73, 91, 95, 111, 117, 135, 146, 148, 152, 182, 190, 216, 222, 228, 234, 252, 270$


Proof

\(\ds 72\) \(=\) \(\ds \map \phi {73}\) Euler Phi Function of Prime
\(\ds \) \(=\) \(\ds \map \phi {91}\) $\phi$ of $91$
\(\ds \) \(=\) \(\ds \map \phi {95}\) $\phi$ of $95$
\(\ds \) \(=\) \(\ds \map \phi {111}\) $\phi$ of $111$
\(\ds \) \(=\) \(\ds \map \phi {117}\) $\phi$ of $117$
\(\ds \) \(=\) \(\ds \map \phi {135}\) $\phi$ of $135$
\(\ds \) \(=\) \(\ds \map \phi {146}\) $\phi$ of $146$
\(\ds \) \(=\) \(\ds \map \phi {148}\) $\phi$ of $148$
\(\ds \) \(=\) \(\ds \map \phi {152}\) $\phi$ of $152$
\(\ds \) \(=\) \(\ds \map \phi {182}\) $\phi$ of $182$
\(\ds \) \(=\) \(\ds \map \phi {190}\) $\phi$ of $190$
\(\ds \) \(=\) \(\ds \map \phi {216}\) $\phi$ of $216$
\(\ds \) \(=\) \(\ds \map \phi {222}\) $\phi$ of $222$
\(\ds \) \(=\) \(\ds \map \phi {228}\) $\phi$ of $228$
\(\ds \) \(=\) \(\ds \map \phi {234}\) $\phi$ of $234$
\(\ds \) \(=\) \(\ds \map \phi {252}\) $\phi$ of $252$
\(\ds \) \(=\) \(\ds \map \phi {270}\) $\phi$ of $270$

$\blacksquare$


Sources