Which of the following options is a prime number?

A prime number is defined as a natural number greater than 1 that has no positive divisors other than 1 and itself. In this case, the number 5 meets this criterion because it can only be divided evenly by 1 and 5. Therefore, it qualifies as a prime number.

On the other hand, the other options do not satisfy the prime number condition. The number 4 can be divided by 1, 2, and 4, making it a composite number. The number 6 has divisors of 1, 2, 3, and 6, also categorizing it as composite. Lastly, 8 can be divided by 1, 2, 4, and 8, confirming it is not a prime number. Hence, among the given choices, 5 is the only prime number.