The factors of a number are defined as numbers that divide the original number evenly or exactly. A factor cannot be a fraction.
A prime number has only 2 factors: 1 and itself. This is because, by definition, a prime number is one that can only be divided by 1 and itself.
13 counts as a prime number. Thus, the factors of 13 are 1 and 13.
ANSWER
The factors of 13 are 1 and 13.