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## #1 2007-03-17 16:16:03

Stanley_Marsh
Member
Registered: 2006-12-13
Posts: 345

I 've though of sth , but don't know whether it's useful or not , but can speed up a little

For example ,  the number 679543

if

we just need to find p.

But the range is still to large , then assume 679543=qpm , then

Assume that  679543=abcd , then

Try , 23,19,17,13,11, 7 5, 3, 2, ,find out that none of them can divide the number , then the number may be the product 3 primes or 2 primes .
I don't know if this can help.

Last edited by Stanley_Marsh (2007-03-17 16:38:33)

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## #2 2007-03-17 16:40:25

Stanley_Marsh
Member
Registered: 2006-12-13
Posts: 345

### Re: About the prime factoring

I think as the number increases , prime become more rare , it'll be easier to do it.

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## #3 2007-03-17 23:37:00

mathsyperson
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Registered: 2005-06-22
Posts: 4,900

### Re: About the prime factoring

I think that would have limited use. You're right that it would help to deduce how many prime factors a number had, but knowing that doesn't help you to find what they are.

Primes do become a bit rarer as you get to higher numbers, but not so much that it becomes easy to try them all out.

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## #4 2007-03-18 07:13:10

Stanley_Marsh
Member
Registered: 2006-12-13
Posts: 345

### Re: About the prime factoring

it can narrow the range and eliminate the number of primes whose product is the number.

I have to work on this some more .

Last edited by Stanley_Marsh (2007-03-18 07:54:36)

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