One.
prime number
A power.
I would call an odd number factor a factor that is an odd number. I would call a number with an odd number of factors a perfect square.
I call it odd.
I call it 1.
A Factor
when it goes into another number
17, being a prime number, has one prime factor, itself. Whether you call that one branch or no branches, it won't be a tree.
It is called a common factor!
It is a factor of the number to be divided
Depends on what the factor is.
It is not possible to give a sensible answer to this question. The greatest common factor (GCF) refers to a factor that is COMMON to two or more numbers. You have only one number in the question so, mathematically, the question does not make sense. If, instead, you consider a number [positive integer] whose greatest common factor is one, then there is only one possibility and that is the number one. So you would call it ONE.