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- Why is 1 not a prime number? 14 answers
I've seen on Maths Is Fun that years ago, 1 was considered as prime, but now, it is not. How did this happen? I know that a prime number has only two factors, 1 and itself, and we have 1, which is also itself. Is this why? Tell me what you think. I also know that this would make the prime factorization too continuous: 1 x 1 x 1 x 1 x 1... x 3 x 3=9 and that would not be good.