What is the least common factor of 18 and 33?

The least common factor of 18 and 33 is 1.

The factors of 18 are 1, 2, 3, 6, 9, and 18.

The factors of 33 are 1, 3, 11, and 33.

The common factors of 18 and 33 are 1 and 3. Therefore, the least common factor (the smallest common factor) is 1.

Note: Because the least common factor of two or more positive integers is always 1, this is not usually asked.

trick question
The least common factor is: 1
The least common factor of any set of integers is 1.