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For a natural number $n$ we denote by $\pi(n)$, for the set of prime divisors of $n$.

Let $q=p^\alpha$ and $q'=r^\beta$ where $r$ and $p$ are odd prime numbers and $\alpha,\beta$ are natural numbers.

Let $p\mid (q'-1)$ and $r\mid (q-1)$. I need to prove that this is impossible that $\pi(q-1)\cup \pi(p)=\pi(q'-1)\cup \pi(r)$?

Is it true?

Thanks for your helps.

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1 Answer

up vote 3 down vote accepted

$q=27=3^3$, $q'=13=13^1$. $3\mid13-1$, $13\mid27-1$. $$\pi(26)\cup3=\pi(12)\cup13=\{2,3,13\}$$

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Many thanks for the answer –  BHZ Jun 20 '13 at 6:49
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