This question variation won’t be asked in the exam, right? The variation in question is “Is 20! + 23 a Prime Number?”

If it can be tested - Can anyone help me understand how to solve for “Is 20! + 23 a Prime Number?” I understand for all numbers less than and equal to 20! because 20! would be a multiple of that number. But how about a prime number > 20? How do I solve then?

No, as they can be difficult to prove (for one, you may end up with a very large factor).

P.S: Please don’t ping us unnecessarily.

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Thanks for the confirmation! Sorry for the tag - deleted it.

for each of the above question you can take something in common

- 10(abc + 1)
- 11(abc +1)
- 13(abc+1)
- but in case of 20! +23 you don’t have a 23 in 20! so you can not take anything in common hence it is not divisible by anything.

This logic cannot be generalised. For example, 571 is prime but 571 + 5 is not prime.

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