64
2,2,2,2,2,2
Prime numbers.
Prime numbers have one distinct prime factor.
Since prime numbers only have one prime factor (themselves), factor trees are unnecessary.
Squares (or cubes or more) of prime numbers have one distinct prime factor, but if you're counting them individually, all composite numbers have at least two prime factors.
The only prime factor of 128 is 2.
The only prime factor of 64 is 2.
The only prime factor of 64 is 2.
The only prime factor of 16 is 2.
31 is the only prime factor of 31.
All prime numbers can be factors.
All prime numbers only have two factors, one and themselves.
Yes, these values are prime numbers since they have only a factor.