Answer:
17 and 19
Step-by-step explanation:
17, 19
15 is composite (5, 3) (15, 1)
16 is composite (8, 2) (4, 4) (16, 1)
17 is prime (17, 1)
18 is composite (9, 2) (6, 3) (18, 1)
19 is prime (19, 1)
20 is composite (2, 10) (4, 5) (20, 1)
