Is 1 a prime number?

[crystal cascade]

I've heard ppl say it is and it isn't, so is it a prime number? :P

[chroot]

No, it's not.

http://www.mathforum.org/dr.math/faq/faq.prime.num.html

- Warren

[crystal cascade]

yeah, I was kind of leaning towards that it's not a prime number, thanks for confirming :)

[mathman]

Excluding 1 from the definition of prime number makes it easier to state many theorems in number theory.

For example, every integer can be factored uniquely into a product of (unique) powers of primes. If 1 was called a prime, its exponent could be anything.