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21 has factors other than 1 and itself, so it is not a prime number. For example, it is divisible by 3. (You can check this by adding the digits of the number: 2 + 1 = 3. If the sum of the digits is divisible by 3, the number is also divisible by 3.) Therefore, 21 is a composite number.
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Can you explain why the prime factorization of 42 is 21 2?
In actual fact, the prime factorization of 42 is not 21 x 2, as 21 is not a prime number. The complete prime factorization of 42 is 2 x 3 x 7.
Is number 21 prime or composite?
number 21 is prime
Is the prime number 21 is a prime number?
21 is a composite number, not a prime, having prime factors 3x7.
Is 21 seven a prime number?
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.
Is 21 and 31 a prime number?
21 is composite number that is a multiple of 3. 31 is a prime number.
