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It looks so wrong (sh.itjust.works)
submitted 5 months ago by [email protected] to c/[email protected]
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[-] [email protected] 22 points 5 months ago

The digit sum of 51 is 6, which is divisible by three. So 51 is also divisible by three. It’s not even hard to see that it’s not prime.

[-] [email protected] 15 points 5 months ago* (last edited 5 months ago)

Yup, my personal prime check is:

  1. Even?
  2. Ends in 5?
  3. Digits sum to 3?

If it fails all three and it's not an "obvious" prime (<20), then it's prime enough for me.

[-] [email protected] 2 points 5 months ago

Also

Ends in 0,

but that's covered by 5 really.

[-] [email protected] 7 points 5 months ago

It's also covered by being even.

this post was submitted on 11 Dec 2024
605 points (95.5% liked)

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