The current Brainliest answer seems to be answering the question "Every integer is a multiple of which number?" rather than the question presented here.
We say that one number is a multiple of a second number if we can get to the first one by counting by the second. For example, 18 is a multiple of 6 because we can reach it by counting by 6's (6, 12, 18). Note that, for any number we want to count by, we can always start our count at 0.
By 2's: 0, 2, 4, 6, 8
By 6's: 0, 6, 12, 18
By 7's: 0, 7, 14, 21
Because we can always "reach" 0 regardless of the integer we're counting by, we can say that 0 is a multiple of every integer.
More formally, we say that some number n is a multiple of an integer x if we can find another integer y so that x · y = n. By this definition, 18 would be a multiple of 6 because 6 · 3 = 18, and 3 is an integer. We can use the property that the product of any number and 0 is 0 to say that x · 0 = 0, where x can be any integer we want. Since 0 is also an integer, this means that, by definition, 0 is a multiple of every integer.
