How many factors dose 123 and 555 have in common?

To find the common factors of 123 and 555, we first need to determine the factors of each number. The factors of 123 are 1, 3, 41, and 123. The factors of 555 are 1, 3, 5, 15, 37, 111, and 555. The common factors of 123 and 555 are 1 and 3. Therefore, they have 2 common factors.