21 is a composite number. A prime number is a number that has exactly two distinct positive divisors: 1 and itself. However, 21 has more than two divisors. The divisors of 21 are 1, 3, 7, and 21. Since 21 can be divided evenly by numbers other than 1 and itself, it is classified as a composite number.
To further understand, let’s break it down:
- Prime Number: A number greater than 1 that has no positive divisors other than 1 and itself.
- Composite Number: A number greater than 1 that has more than two positive divisors.
In the case of 21, it can be divided by 3 and 7, which means it has divisors other than 1 and itself. Therefore, 21 is not a prime number but a composite number.