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can someone please describe me why only the perfect square has odd number of factors.why does other number not has odd numbers of factors? I understand it but don't find any mathmetical proof.Please help me

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For a given number $n$ we can group its divisors in pairs $(d,\frac nd)$, except that if $n=m^2$ this would pair $m$ with itself.

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please explain briefly – user100315 Oct 14 '13 at 17:58
@FRM, I strongly recommend you write out examples. For this sort of mathematics, thinking about examples and non-examples is highly illuminating and will generally lead you to understand the proof. – Ted Shifrin Oct 14 '13 at 21:00

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