# Why perfect square has odd number of factors

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