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.
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Factors of 21 are 1, 3, 7, and 21. 21 is a compositenumber because it has more factors than just 1 and itself.
number 21 is prime
21 is a composite number, not a prime, having prime factors 3x7.
Who says it is? 21 is a composite number!
21 is composite number that is a multiple of 3. 31 is a prime number.
19 is a prime number. Its only factors are 1 and 19. 21 is a composite number. Its factors are 1, 3, 7, and 21. 23 is a prime number. Its only factors are 1 and 23.