991 is already prime. No tree is required.
991
no
The factor tree is as follows: 114 57,2 19,3,2
No.
yes
13 is a prime number. It doesn't have a tree because its only prime factor is itself.
No you cannot. You might want to try the factor tree for 27.
15,3 3,5,3
prime factors
39 3,13
119 7,17
35 5,7