what is a prime number?

by **cindyqtran** Fri Jun 22, 2007 8:55 pm

Hi, I have a question.2, 3, 5, 7... are all prime numbers. But is -7, -13 prime numbers?

Can negative numbers be primes because they are a multiple of itself and 1.

Thanks.

by **StaceyKoprince** Fri Jun 22, 2007 9:06 pm

Excellent question Negative numbers are not prime, for no other real reason than that... somebody thought of prime numbers before somebody else thought of negative numbers. So, built into the definition is that primes are positive. :) (Technically, there's some explanation that -1 is a factor and so on... but really it's just because nobody wanted to go change everything after some enterprising mathematician started playing with negative numbers.)