Answer:
16 and 3
Step-by-step explanation:
A prime number has only 2 factors, 1 and itself
2, 5 and 7 meet this criteria and are prime, however
factors of 16 are 1, 2, 4, 8, 16
16 does not meet the criteria and is not prime
--------------------------------------------------------
The factors of 18 are 1, 2, 3, 6, 9, 18
The only one of these factors which is prime is 3