What are factors of 19 and 20?

Answer 1

The term common factors specifically refers to the factors shared by two or more numbers. Since 19 is a single number, you could say that it shares all of its factors with itself.
19 is a Prime number. It is only evenly divisible by itself and one.

Answer 2

The PROPER factor of 19 is 1 and just 1. Since 19 is a prime number its only proper factor is 1. Any prime number only has 1 proper factor which is 1.

Answer 3

1, 19

1, 2, 4, 5, 10, 20

Answer 4

1,19

1,2,4,5,10,20

Answer 5

1 and 19

Answer 6

1 and 19