mersenneforum.org How to determine if a large number is prime? Is this True?
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2020-12-12, 05:16   #1
ONeil

Dec 2017

24×3×5 Posts
How to determine if a large number is prime? Is this True?

Is the below statement True?

Quote:
 You check every prime number that's less than the square root of the number you're concerned with. The square root of 941 is 30.67, so check every prime number up to 29. If none of them divide 941, then it is prime. https://www.reddit.com/r/learnmath/c...mber_is_prime/

 2020-12-12, 05:25 #2 CRGreathouse     Aug 2006 32×5×7×19 Posts Less than or equal to, yes. (The bold part is necessary in case you encounter the square of a prime.) But this is a very slow method and much better ones are known even for quite small numbers.
 2020-12-13, 13:35 #3 kriesel     "TF79LL86GIMPS96gpu17" Mar 2017 US midwest 7·17·43 Posts Last fiddled with by kriesel on 2020-12-13 at 13:38

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