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Thread: Test for primes

  1. #1 Test for primes 
    New Member
    Join Date
    Apr 2013
    Hello forum, I am recently graduated from high school and I'm trying to stock up on my math skills.

    I was wondering if there is any way to check to see if a number is a prime number. Besides simply dividing it by every number between itself and 1.
    e.g. is 12348575574747733 a prime number? How can you tell?

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  3. #2  
    Join Date
    Jun 2012
    Well, if you have a computer, this wouldn't be so hard. But mathematically, there is no easy way to verify whether any number is a prime number or not.

    No, , it's not a prime number.

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  4. #3  
    Brassica oleracea Strange's Avatar
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    Oct 2011
    Quote Originally Posted by knowlege seeker View Post
    Besides simply dividing it by every number between itself and 1.
    The first optimization is to realise that you only need to test numbers between 1 and square root of the number. Then you can improve it further by not testing every multiple of 2 and 3, for example (if something is divisible by 3 then it is going to be divisible by every multiple of 3).

    See here for a whole lot more information: Primality test - Wikipedia, the free encyclopedia
    missarane likes this.
    ei incumbit probatio qui dicit, non qui negat
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