.The congruence is true. Can you conclude that is a prime number?

Of course not: why would anyone conclude such a thing?? Of course, it's pretty easy to check directly that , but even without this

we couldn't conclude that: for example, ...can we conclude 15 is prime? ...is 9 a prime?

About what you wrote below: " ...is in the format of FLT..." do you mean Fermat's Little Theorem? What is in this format??

Tonio

So would the answer be that since is in the format for FLT then must be prime right?