If the integer n is divided by m, the result is an integer with no remainder, then we call it a factor. It should be noted that this relationship only holds if the dividend, divisor and quotient are integers and the remainder is zero.

Instead, we call it a multiple of. There is a saying that "factors are not limited to positive and negative", but usually only positive factors are taken. (-1,) n (and -n) These numbers are called obvious factors of n, which can be expressed by factor _ multiple or multiple ≡0(mod factor) (see congruence), but when using the latter, the factor must be a positive factor. The vertical line in the factor _ multiple formula is an integer symbol.

Its uniform code value is U+2223. For example, 42=6x7, so 7 is a factor of 42. Writing 7_42 is also 42=0(mod7). Scientists Gao Deng and Gao Zhezhong in the Northern Song Dynasty put forward the conclusion of this century. 1942, confirmed by Americans.