Identify the Prime Number Among the List: A Basic Number Theory Challenge

Let's determine which of the given numbers is a prime number. A prime number is a natural number greater than 1 that is only divisible by 1 and itself.

We have the following numbers to consider: $22, 23, 20,$ and $27$.

• 22: This number is divisible by 1, 2, 11, and 22. Therefore, it is not a prime number since it has divisors other than 1 and itself.
• 23: This number is only divisible by 1 and 23. It satisfies the definition of a prime number, as it has no divisors other than 1 and 23.
• 20: This number is divisible by 1, 2, 4, 5, 10, and 20. It has divisors other than 1 and itself, making it not a prime number.
• 27: This number is divisible by 1, 3, 9, and 27. Like the others, it is not a prime number because it has divisors other than 1 and itself.

Thus, after evaluating all options, we find that only $23$ is a prime number.

Therefore, the solution to the problem is $23$.