105 :D
3, 6, 9, 12, 15, 18, 21
You just divide it by 21 and if there is no remainder then it went in evenly.
1, 3, 7, 21.
67 is a prime number, but 21 isn't. A prime number can only be evenly divided by '1' and itself. 21 can be evenly divided by 1, 3, 7, and 21.
Only the number one.
21
The number 7
Factors are those numbers which can be evenly divided into a number. The factors of 21 would be 1, 3, 7, 21 The factors of 28 would be 1, 2, 4, 7, 14, 28 The factors of 15 would be 1, 3, 5, 15
0.21 If you want to find what goes into 21 100 times evenly all you have to do is divide 21 by 100.
There is an infinite number of common multiples for 21 and 15. A common multiple of any two or more numbers is any number into which each of two or more numbers can be divided evenly (zero remainder).
27 is composite. 27 = 3 * 3 * 3 = 3315 is composite. 15 = 3 * 521 is composite. 21 = 3 * 723 is a prime number. It is only evenly divisible by itself and one.
3