Question

which is a composite number? 21 43 29 37

Explanation:

Step1: Recall composite number definition

A composite number is a positive integer that has at least one positive divisor other than 1 and itself. A prime number has only 1 and itself as divisors.

Step2: Analyze 21

Factorize 21: \(21 = 3\times7\). So, 21 has divisors 1, 3, 7, 21. Thus, it is composite.

Step3: Analyze 43

Check divisors of 43. It is only divisible by 1 and 43. So, 43 is prime.

Step4: Analyze 29

29 is only divisible by 1 and 29. So, 29 is prime.

Step5: Analyze 37

37 is only divisible by 1 and 37. So, 37 is prime.

Answer:

21