KTEST 6 2027 Practice Test

Which of the following is a prime number? 15, 21, 29, 33.

15 21 29 33

Correct Answer:

Explanation:

A prime number is a number greater than 1 that has exactly two divisors: 1 and itself. To check primality, you only need to test divisibility by primes up to the square root of the number. - 15 has divisors 1, 3, 5, and 15, so it has more than two divisors and isn’t prime. - 21 is divisible by 3 and 7, so it’s not prime. - 29 is not divisible by 2, 3, or 5. Since the square root of 29 is about 5.38, you only need to check primes up to 5, and none divide 29. Therefore, its only divisors are 1 and 29, so it is prime. - 33 is divisible by 3 and 11, so it isn’t prime. Thus, 29 is the prime number.

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