Re:Emirp Primes
by 0x8BADF00D on Friday May 03, 2019 @01:19AM
(#19815784)
Is there a better way to check for an emirp other than checking if the number is prime, and then checking if its reverse is also prime?
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I can think of a couple of things off the top of my head:
- You can reject numbers that start with 2,4,5,6 or 8 since their reverse won't be prime.
- If you're searching through a range of numbers for emirps avoid checking for the same pair twice. For example if you start at 1 and check for emirps, by the time you're checking 311 you've already checked 113 so you don't need to check 311.