Twenty-one is divisible by 1, 3, 7, and 21. These are the factors of 21.
Factors of 21 Explained
The factors of a number are the integers that divide evenly into that number. In other words, when 21 is divided by any of its factors, the result is a whole number with no remainder.
- 1: 21 / 1 = 21
- 3: 21 / 3 = 7
- 7: 21 / 7 = 3
- 21: 21 / 21 = 1
Why These Are the Factors
To find the factors of any number, you can systematically test integers starting from 1 and going up to the square root of the number (in this case, approximately 4.58). If an integer divides evenly into the number, it's a factor. The corresponding quotient is also a factor.
Summary
Twenty-one is perfectly divisible by 1, 3, 7, and 21. These are its only positive integer factors.
