Because: 1*80=80, 2*40=80, 4* 10=80, 5* 16=80, 8* 10=80.
Factor, a mathematical term.
If a*b=c(a, B and C are all integers), then we call A and B factors of C. It should be noted that this relationship only holds when the dividend, divisor and quotient are integers and the remainder is zero. On the contrary, we call c a multiple of a and b, and we don't consider 0 when studying factors and multiples.
In fact, factors are generally defined as integers: let a be an integer and b be a non-zero integer. If there is an integer Q that makes A=QB, then B is a factor of A, denoted as B | A ... but some authors do not require B≠0.
For example, 2X6= 12, and the product of 2 and 6 is 12, so 2 and 6 are factors of 12. 12 is a multiple of 2 and also a multiple of 6.
3X(-9)=-27, 3 and -9 are all factors of -27. -27 is a multiple of 3 and -9.