21 = 3x7, and so is not prime, as it can be expressed as the product of multiple prime numbers
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21 is not a Prime number. It is divisible by 3 and 7, in addition to 1 and itself.
number 21 is prime
21 is a composite number, not a prime, having prime factors 3x7.
21 has two prime factors.
factors of 21: 3, 7 prime factors of 21: 3, 7
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.