Euler Phi Function of 252
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Example of Use of Euler $\phi$ Function
- $\map \phi {252} = 72$
where $\phi$ denotes the Euler $\phi$ Function.
Proof
From Euler Phi Function of Integer:
- $\ds \map \phi n = n \prod_{p \divides n} \paren {1 - \frac 1 p}$
where $p \divides n$ denotes the primes which divide $n$.
We have that:
- $252 = 2^2 \times 3^2 \times 7$
Thus:
\(\ds \map \phi {252}\) | \(=\) | \(\ds 252 \paren {1 - \dfrac 1 2} \paren {1 - \dfrac 1 3} \paren {1 - \dfrac 1 7}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds 252 \times \frac 1 2 \times \frac 2 3 \times \frac 6 7\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds 6 \times 1 \times 2 \times 6\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds 72\) |
$\blacksquare$