CPhill is right,
31, 37 are prime.
32 has only 1 prime factor".......... 2
33=3 x 11
34=17 x 2
35=7 x 5
38=19 x 2
39=13 x 3
this would only leave 36= 2^2 x 3^2
soo...... The prime factors are 2 and 3...... And these, indeed, sum to 5!!!! So he is right