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I have been told that there is some interesting mathematics to why the number 1 is not prime. Can someone explain why one is not a prime number?

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    $\begingroup$ By definition, a prime must have only a factor of 1 and itself. Because 1 has no other factor other than itself, it is therefore not prime. $\endgroup$ – bjd2385 Feb 6 '15 at 16:34
  • $\begingroup$ For how long did you search before posting this question? $\endgroup$ – user147263 Feb 6 '15 at 16:34
  • $\begingroup$ @FamousBlueRaincoat Thanks, I thought this might be a duplicate... $\endgroup$ – bjd2385 Feb 6 '15 at 16:35
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Because a prime number is a number that has exactly two distinct positive divisors.

Examples:

  • $2$ can be divided by $1$ and $2$

  • $11$ can be divided by $1$ and $11$

  • $1$ can be divided by $1$ and... $1$ so it is not prime.

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