All but 31 and 37 are composite.
Only 63 is a composite. 63 = 3 x 3 x 7 The other three numbers (13, 31, 61) are all prime numbers.
All of them except for 31, 37, 41, 43 and 47 which are prime numbers.
31,37 are not composite
A composite number is a number with more than two positive integer factors (itself and one). Other than these two numbers, the positive integer factors of 155 are 5 and 31.
31 is not composite.
An integer greater than 1 can be composite or prime but not both. So 31 cannot be a composite prime.
31 is prime. 32 and 33 are composite.
31 and 61 are prime, the rest composite.
No.
31 is PRIME.
31 is prime.
4 is composite, 31 is prime.
31 and 47 are prime, the rest composite.
31, 47 and 103 are prime. The rest are composite.
21 is composite as 3 times 7 is 21 31 is prime
31 is prime.