When it is a factor of that particular number.
I think you might mean "multiple." If the sum of a number's digits is a multiple of 9, the original number is as well. If you want to know how you know if a number is a factor of 9, memorize the numbers 1, 3 and 9.
A factor is what goes into a number, a multiple is what a number goes into. 3 is a factor of 9 27 is a multiple of 9.
No. A number cannot be both a factor and a multiple of another number. A number can be multiple and factor of itself, but nothing else.
No. A factor goes into a number. A number goes into a multiple. They have an inverse relationship in the sense that if A is a multiple of B, then B is a factor of A.
One is a multiple and a factor.
They have a converse relationship. A factor is a number that divides into another, with no remainders. A multiple is something that can be multiplied by another number, to reach the original number that you had. Thus: Original number / a factor = a multiple Multiple * (the correct factor) = original number. "the correct factor", because most number have more than one factor. But only one factor * multiple will give the original number.
There is no multiple of 10 that's a factor of 45.
Which number is a factor of 10 , but not a multiple of 5
Only if the multiple, the factor and the original number are all the same. 10 is a multiple and factor of 10.
The number is 18, It is even number, it is factor of 198 and multiple of 9
16 is both a factor and a multiple of itself.