Is 111 composite

Answer 1

Yes. This can easily be determined by trying out divisibility rules.

Since it is not an even number, 111 is not divisible by 2.

However, since its digit sum (1+1+1=3) is divisible by 3, 111 is divisible by 3.

The prime factorization of 111 is 3*37.

Note: If a factor cannot be found so quickly, remember that you only have to test prime numbers up to the square root (why? once you get past the square root, if another factor exists its "pair" will have to be one of the primes below the square root, which would already have to be tested by you beforehand). In this case, you could test primes up to 11 (since 112=121, which is the next highest perfect square greater than 111)