The single number directly between those two numbers is 18.
3
17... and 19 !
The prime factors of 34 are 2 and 17, and 2 + 17 = 19.
11 13 17 19.
17, 19, 23, 29, and 31
11, 13, 17, 19
11 13 17 19.
11 13 17 19
11, 13, 17, 19
11 13 17 19.
The prime numbers between 10 and 20 are 11, 13, 17, and 19.
17, 19, 23, 29, and 31