Faster way to check if n is prime?

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Number Theory

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Hi,

I recently had a theory regarding checking whether n is prime or not (although I don't think I'm the first one to come up with that theory) how would I prove this theory and if there was someone before me who was it?

The standard method I have been thought of checking if n is prime is checking every number until n. If n is divisible by at least one number in this range n isn't prime.

My theory is that you only need to check every number until ⌈√n⌉ 1. The only number I could find that doesn't abide by this "rule" is 2.

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Posted: 4 months ago
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