Re: factorization

On Thu, 17 May 2007 13:23:31 GMT, "Douglas A. Gwyn" <DAGwyn@xxxxxxxx>
wrote:

Mirror wrote:
All prime numbers - except 2 and 5 - have as their last digit, either
1 or 3 or 7 or 9.

Duh.

We notice that the last digit of the multiplication of two prime
numbers is also 1,3,7 or 9. How is that ?

False: 5 * 7 = 35, last digit is 5
2 * 3 = 6, last digit is 6

...
this fact can possibly lead to a factorization in polynomial time or
even faster.

Many people have tried a more sophisticated analysis of the low-
and high-order digits (usually bits, rather than decimal digits)
but haven't yet been able to turn the idea into a practical
factoring algorithm.

did you read that 'except 2 and 5' ? it means they are excluded as
prime list, because if the product is either a 2 or a 5, it would be
obvious because the last digit would either be even or 5.

Duh.
.

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