Reid Nichol a icrit :
--- Jean-So?=bastien Bour <[EMAIL PROTECTED]> wrote:
Matthias Kilian a icrit :
a) 4 is the first non-prime, at least according to factor(6).
No, it is 1 :)
Explanation : a prime number can only be divided by two different
numbers : 1 and itself. 1 can only be divided by one number,
therefore it is not prime.
Wrong.
You got the definition of what a prime number is wrong. A prime number
is defined as a positive integer greater than one which has positive
divisors 1 and itself, only.
Please note that using your definition 7 is not prime because -7, -1, 1
and 7 all divide 7.
I suggest at least looking into elementary number theory before making
such statements again.
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No no not wrong, indeed I didn't talk about being positive. But being
prime is being positive (should have said it I agree) and have EXACTLY
TWO different divisors. And if 1 were prime you wouldn't have only one
unique decomposition in prime numbers ;) (for exemple, is 45 = 3x3x5 or
1x3x3x5 or 1x1x1x3x3x5 or... ?) It would crush many things down about
arithmetics.
Luckily I have learnt some things during my two year special scientific
studies (heard about "Classes priparatoires" in France ?) and this is
one of those.
