(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

let n be an integer . Prove the congruence below.

n^21 [itex]\equiv[/itex] n mod 30

2. Relevant equations

n^7 [itex]\equiv[/itex] n mod 42

n^13 [itex]\equiv[/itex] n mod 2730

3. The attempt at a solution

to prove 30| n^21-n，it suffices to show 2|n^21-n,3|n^21-n,5|n^21-n

and how to prove them?

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# Homework Help: Number theory problem about Fermat 's little theorem

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