Well, 18 and 3 (both factors of 36) add up to 21. As well, the factors 12 and 9 add up to 21.
2 AND 21 there is only one factor that adds up to 23 and if you multiple 21 times 2 =42
21
364
The factors of 21 are 1, 3, 7 and 21. No two of them add up to 21.
Factors are numbers you can multiply together to get another number. Therefore, all the factors of 21 are as follows: 1,3,7,21.
25
-25
41
Factors are numbers you can multiply together to get another number. 21: (1, 21) (3, 7)
48, because it adds another 2 to the prime factorization.
-21 and -1
It is when the prime factors of whole number are multiplied together that they equal that number. For example the prime factors of 21 are 3 and 7 so 3*7 = 21