What is the least common factor of 42 56 and 140?

The factors of 42 are 1, 2, 3, 6, 7, 14, 21, and 42.

The factors of 56 are 1, 2, 4, 7, 8, 14, 28, and 56.

The factors of 140 are 1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 70, and 140.

The common factors of 42, 56, and 140 are 1, 2, 7, and 14. Therefore, the least common factor (the smallest common factor) is 1.
The GCF is 14.