One could be part of a factor pair.
One such factor pair is 10 and 80.
factor pair = 1512,1 factor pair = 756,2 factor pair = 504,3 factor pair = 378,4 factor pair = 252,6 factor pair = 216,7 factor pair = 189,8 factor pair = 168,9 factor pair = 126,12 factor pair = 108,14 factor pair = 84,18 factor pair = 72,21 factor pair = 63,24 factor pair = 56,27 factor pair = 54,28 factor pair = 42,36
That happens when one of the numbers is a factor of the other.
Numbers with more than one factor pair are composite numbers.
factor pair = 650,1 factor pair = 325,2 factor pair = 130,5 factor pair = 65,10 factor pair = 50,13 factor pair = 26,25
A number with only one factor pair is........ a prime number for example 11 the only factor pair is one times 11.
factor pair = 36,1 factor pair = 18,2 factor pair = 12,3 factor pair = 9,4 factor pair = 6,6
The factor pair for 31 is 1*31. Since 31 is prime, it has only one factor pair.
factor pair = 90,1 factor pair = 45,2 factor pair = 30,3 factor pair = 18,5 factor pair = 15,6 factor pair = 10,9 Doctor Chuck Mathdoc
One only has one factor. If you have to, you can use (1,1)
The factor pair of 13 is 1, 13. It only has one factor pair since it's a prime number.
191 is prime. It has one pair of factors, one and itself.