Which of the following numbers is prime: 11, 21, 25, 33?

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Multiple Choice

Which of the following numbers is prime: 11, 21, 25, 33?

Explanation:
A prime number is a number greater than 1 that has exactly two distinct divisors: 1 and itself. 11 fits because it cannot be divided evenly by any integer between 2 and 10; its only divisors are 1 and 11. The other numbers have additional divisors: 21 is divisible by 3 and 7, 25 is divisible by 5, and 33 is divisible by 3 and 11. So only 11 has exactly two divisors, making it prime. If you test up to the square root of 11 (about 3.3), you’d check 2 and 3—neither divides 11, confirming its primality.

A prime number is a number greater than 1 that has exactly two distinct divisors: 1 and itself. 11 fits because it cannot be divided evenly by any integer between 2 and 10; its only divisors are 1 and 11. The other numbers have additional divisors: 21 is divisible by 3 and 7, 25 is divisible by 5, and 33 is divisible by 3 and 11. So only 11 has exactly two divisors, making it prime. If you test up to the square root of 11 (about 3.3), you’d check 2 and 3—neither divides 11, confirming its primality.

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