To find the mean (average) of the numbers 28, 40, 53, 39, and 45, you follow these steps:

1. Add all the numbers together:
   $28 + 40 + 53 + 39 + 45 = 205$

2. Count the total number of values:
   There are 5 numbers in total.

3. Divide the sum by the number of values:
   $\text{Mean} = \frac{205}{5} = 41$

So, the mean of the numbers is 41.

Would you like a more detailed explanation or help with another question? Here are some related questions you might find interesting:

1. How do you find the median of a set of numbers?
2. What is the difference between mean, median, and mode?
3. How do you calculate the range of a set of numbers?
4. What happens to the mean if you add or remove a number from the dataset?
5. Can you find the weighted mean for a set of numbers?

Tip: When calculating the mean, always double-check your sum and division to ensure accuracy!