So in my math class, the solution for finding the standard divisor is:
20,000 / 18 = 1, 111.111111
The class round it to the whole number, so 1,111. We still get the same number of representatives and standard quota. Our reason for using the whole number is due to the fact we're dealing with people. There are no fractional numbers when it comes to dealing with people. However, she marked it wrong and said she wanted it as 1, 111.11 because she wants to copy everything in the calculator but its missing 4 more decimal places. -_-
So should standard divisors be whole numbers when it comes to dealing with people or no?
The standard divisor should not be rounded. It does not represent a number of people which you are going to use as a final answer to a question in which a fractional person would be meaningless. It is instead an intermediate stage in the calculations which will be plugged into later calculations. Rounding the standard divisor will make those later calculations (of the standard quotas) inaccurate.
To put it another way, the standard divisor represents the average number of people per seat. There is no reason for an average to be an integer, even if it is an average of integer quantities. For instance, the average household in the US has about $2.6$ people. Obviously there are no actual households that have exactly $2.6$ people, but some households have $2$ (or less) and others have $3$ (or more) and it ends up averaging out to $2.6$.