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in reply to Re: Re: Prime Number Finder

Whether or not 1 is prime is a question of definitions.

While I admit that it makes more sense to me to say that 1 is not a prime, there is certainly not universal agreement on it. In particular (as I discovered when I took some advanced number theory courses) a number of the people who undertook to compute long lists of primes started their lists with 1. After a while you learn not to be too dogmatic about it. (Though I have to say that there is far more agreement that 1 is not prime than there is on, say, whether 0 is a natural number.)

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Re: Re (tilly) 3: Prime Number Finder
by I0 (Priest) on Feb 22, 2002 at 05:56 UTC
"Whether or not 1 is prime is a question of definitions."
Indeed. It is not prime by definition.

This is a useful definition since it allows integers to have a unique prime factorization.

(Less controversially, 0 is not prime, although it is also listed by the program which prompted this comment)
You claim that 1 is not a prime by definition, and This is a useful definition since it allows integers to have a unique prime factorization. But note:
```6 = 2 * 3 = 3 * 2 = (-2) * (-3) = (-3) * (-2)