Question

Which number is not composite 2,9,15,21

Answer 1

2 is the only number that is prime. The others are composite because they have factors other than 1 and itself.

Answer 2

A composite number is divisible by other numbers, including 1 and itself.

Opposite of composite is prime, so we need to look for the PRIME number.

2 is a prime number because it is only divisible by 1 and itself(2).

Answer: 2