21 is a composite number
31 and 61 are prime, the rest composite.
number 21 is prime
Composite
Composite.
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.
Composite, 21=3*7
21 is a composite number, not a prime, having prime factors 3x7.
Who says it is? 21 is a composite number!
21 is a composite number.
21 is a composite number.
27 is composite. 27 = 3 * 3 * 3 = 3315 is composite. 15 = 3 * 521 is composite. 21 = 3 * 723 is a prime number. It is only evenly divisible by itself and one.