13 is already prime. It doesn't need a tree.
56 28,2 14,2,2 7,2,2,2
484 242,2 121,2,2 11,11,2,2
675 225,3 75,3,3 25,3,3,3 5,5,3,3,3
720 360,2 180,2,2 90,2,2,2 45,2,2,2,2 15,3,2,2,2,2 5,3,3,2,2,2,2
77 7,11
15 3,5
1,270,2,135
18 9,2 3,3,2
18 9,2 3,3,2
23 is a prime number. No prime factorization. No tree.
13 is already prime. It doesn't need a tree.
188 94,2 47,2,2
75 25,3 5,5,3
275 55,5 11,5,5
39 3,13
18 6 x 3 (2x3) x 3 Since 2 and 3 are prime numbers, the factor tree is complete. An alternate version of the factor tree for 18 is: 18 2 x 9 2 x (3x3)