The greatest remainder when you divide by 21 is 20. This is because the remainder is always less than the divisor. Therefore, when a number is divided by 21, the possible remainders range from 0 to 20, with 20 being the highest.
4
1000
47
9
The greatest possible remainder is 11.
If you're dividing a whole number by 2, then the greatest possible remainder is 1.
4
11
2
It is: 457/21 = 21 with a remainder of 16
7.
17