The prime factorization.
13 is already prime, no tree required.
Use a factor tree. 55 5,11
Their at the bottom of the tree because the hole point of a factor tree is to find the prime factorization of the number, so it would be at the bottom of the tree.
With a factor tree, yes.
83 is prime. No tree.
IT IS PRIME there is no factor tree
If completed correctly, the bottom branch of a factor tree will be the prime factorization of the number at the top.