Among the numbers provided, the number 17 is a prime number.
A prime number is a number greater than 1 that has no positive divisors other than 1 and itself. In other words, it cannot be evenly divided by any other number.
Let's examine each number to determine if it is prime:
1. 12: This number is not a prime number because it can be divided evenly by 2, 3, 4, 6, and 12.
2. 28: This number is not a prime number because it can be divided evenly by 2, 4, 7, 14, and 28.
3. 17: This number is a prime number because it cannot be divided evenly by any number other than 1 and 17. Therefore, it has only two positive divisors, making it a prime number.
4. 18: This number is not a prime number because it can be divided evenly by 2, 3, 6, 9, and 18.
Based on this analysis, we can conclude that the number 17 is the only prime number among the given numbers.