Results 1 to 2 of 2

Math Help - Prime factor calcuation

  1. #1
    Jan 2009

    Prime factor calcuation

    Hi, I calculated the prime factors of the following numbers:

    1. 3211

    2. 310

    3. 4139
    This is prime number

    I took me a few calculations to reach the answers - I usually start with the lowest prime number and use division, is there any way to use fewer calculations?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member Bacterius's Avatar
    Nov 2009
    Ah, factorizing numbers quickly is considered like a very, very hard problem indeed. For mental calculation I think there is nothing more effective than checking division with every prime number up to \sqrt{n} where n is the number to factorize. However you could maybe spend a couple of seconds looking at the number before and trying to see if it doesn't have some particular structure (like an obvious multiple of 11), etc ... You might also like to do it the other way round : start at \sqrt{n} and go down until you reach 1, it can reveal useful if the number has only two prime factors that are near each other.

    This is for mental calculation ; for computer calculation there are much, much more effective methods going around, that would crunch most numbers you could ever think of. But they can get quite complicated to understand if you are not familiar with algorithms.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. A prime factor problem.
    Posted in the Number Theory Forum
    Replies: 8
    Last Post: May 1st 2011, 03:15 AM
  2. How do you factor an un-prime quadratic?
    Posted in the Algebra Forum
    Replies: 3
    Last Post: March 29th 2011, 08:30 PM
  3. Factor or Prime?
    Posted in the Algebra Forum
    Replies: 2
    Last Post: May 4th 2008, 02:08 PM
  4. Prime factor problem
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: January 29th 2008, 11:12 AM
  5. Find a prime factor of 99!-1
    Posted in the Number Theory Forum
    Replies: 2
    Last Post: June 16th 2005, 05:19 AM

Search Tags

/mathhelpforum @mathhelpforum