15
3,5
15 3,5 Not much of a tree. More like a factor shrub.
1,350 / \ 135*10 / \ / \ 9*15 2*5 / \ / \ 3*3 3*5
77 7,11
1,270,2,135
23 is a prime number. No prime factorization. No tree.
13 is already prime. It doesn't need a tree.
275 55,5 11,5,5
188 94,2 47,2,2
75 25,3 5,5,3
39 3,13
15 3, 5
5,3