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Q: Why is 21 a prime number?

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number 21 is prime

21 is a composite number, not a prime, having prime factors 3x7.

There is an infinite number of prime numbers that are greater than 21. The next prime number after 21 is 23.

11 is a prime number but 21 is not a prime number as it is divisible by 3.

21 is the product of two prime numbers, three and seven. A prime number is defined as a number divisible only by one or itself. So ... NO ... 21 is not a prime number.

21 is composite number that is a multiple of 3. 31 is a prime number.

A prime number is any integer evenly divisible by only itself, and the number 1. Since 21 is divisible by 3 and 7, it is a composite number, not a prime number.No, 21 is not a prime number.21 is divisible by 1, 3, 7, & 21No. 21=3*7

21 is a Composite Number. A prime number is a whole number that only has two factors which are itself and one. A composite number has factors in addition to one and itself. 21 is divisible by 3 and 7.

3 * 7 = 21 21 is not prime

no, 21*21=441

21 is a composite number

No. The only factors of a prime number are 1 and itself. The only way that 21 could be a factor of a prime number is if it were a prime number, but it is not because 21 is also divisible by 3 and 7.

No.

No.

No, 21 is not a prime number.

21 has two prime factors, 3 and 7.

3 is a prime factor of 12 and of 21.

17 is a prime number, but 21 is not (21 = 3 * 7).

21 is not a prime.

no. 7 x 3 = 21

21 is a composite number.

21 is a composite number.

3 x 7 = 21, since both factors are prime, that is the prime factorization of 21.

The prime factorization of 21 is 3 x 7.

31 is a prime number.