The number below that is a prime number is 83.
Here's why:
1. Prime numbers: Prime numbers are whole numbers greater than 1 that have only two factors, which are 1 and the number itself. In other words, prime numbers cannot be divided evenly by any other numbers.
2. Checking the numbers: Let's check the given numbers one by one.
a. 69: This number can be divided evenly by 1, 3, 23, and 69, so it is not a prime number.
b. 83: This number can only be divided evenly by 1 and 83, so it is a prime number.
c. 105: This number can be divided evenly by 1, 3, 5, 7, 15, 21, 35, and 105, so it is not a prime number.
d. 80: This number can be divided evenly by 1, 2, 4, 5, 8, 10, 16, 20, 40, and 80, so it is not a prime number.
3. Conclusion: Out of the given numbers, 83 is the only one that meets the criteria of being a prime number because it has only two factors, 1 and 83.
Therefore, the number 83 is a prime number.