Factors of numbers usually come in pairs. Thus, most numbers have an even number of factors.


Some special numbers, though, have an odd number of factors.

Find a copy of the chart below, in the folder at the computer desk. Under each number, list all the factors of the number.
Use pairing to help you find all of the factors.
Start with 1 for each number and end with the number itself, listing the factors in order.

When you are finished with all fifty numbers, circle all of the numbers (in the original typed list) that have exactly two factors.

What do we call this set of numbers? __________________

Put a square around all of the numbers (in the original typed list) that have an odd number of factors.

What do we call this set of numbers? __________________


One of the numbers, 18, is done for you, as an example.

Your work will be evaluated on neatness, accuracy, and answering the questions correctly.