The bottom branch of a factor tree consists entirely of prime numbers.
Prime numbers don't have factor trees. So if you can create a tree, your number's composite.
If completed correctly, the bottom branch of a factor tree will be the prime factorization of the number at the top.
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.
A Factor Tree
factor tree
The purpose of a factor tree is to notate the process of finding the prime factorization. If a number is already prime, a factor tree is not necessary.
The purpose of a factor tree is to divide a number into prime factors. 1 is not a prime number.
83 is a prime number and doesn't have a factor tree since its only prime factor is itself.
199 is a prime number. It does not have a tree since it only has one prime factor, itself.
19 is prime. No tree.
23 is a prime number. No prime factorization. No tree.
13 is a prime number so it doesn't have a factor tree.
There is no factor tree nor factors of 57 as it is a prime number.
2 is a prime number; no factor tree.
13 is a prime number. It doesn't have a tree because its only prime factor is itself.
41 is a prime number and doesn't have a tree because it only has one prime factor: itself.
Prime numbers don't have factor trees. So if you can create a tree, your number's composite.