Answer:
13
Explanation:
13 is a prime number because it is only divisible by itself, 13, and 1. 13 = 13 * 1
14 is not because it is divisible by 2 and 7. 7*2 = 14
15 is not because it is divisible by 5 and 3. 5*3 = 15
And 16 is not because it is divisible by 4, 8, and 2. 4*4 = 16 and 8*2 = 16.