Answer : 3 21 Explanation : Answer: C) 21 Explanation: A prime number is a whole number greater than 1 whose only factors are 1 and itself. Factors of 5 are 1, 5Factors of 11 are 1, 11Factors of 21 are 1, 3, 7, 21Factors of 37 are 1, 37. Hence, according to the definition of a prime number, 21 is not a prime number as it has more than two factors.

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