What are some common factors of 25 and 250?

1,5,25.

I do not think there are more.

In order to find common factors between 25 and 250, you need to list everything that has a product of their respective numbers like so:

1,5, 25

1,5,10,25,50,250

The common factors between 25 and 250 are 1, 5 and 25