LogFAQs > #942016249

It's easy.

3 and 7 are prime numbers, so they're only divisible by themselves or by 1. That means that the composite number formed by them will only be divisible by said composite number. There is a specific name to that law but I don't remember what it's called. It's been 12 years since I last touched a math related book or had the need to practice.

Try it with 27 for example (2 is also prime).

27*4=108
081/27=3
810/27=30

I'm too bored atm to try with the other prime numbers, but I think* the lower prime number must be first and the higher number must be second and there may be other factors involved. So I think 27 works but 72 doesn't, I don't know, my head already hurts and this was a small thing I remembered.

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