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**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)*

Numbers are the essence of the Universe

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

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

Numbers are the essence of the Universe

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

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.

Why did the vector cross the road?

It wanted to be normal.

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

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)*

Numbers are the essence of the Universe

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