What is the greatest common factor of 20 81 and 132?

Factors of 20: 1 2 4 5 10 20 Factors of 81: 1 3 9 27 81 Factors of 132: 1 2 3 4 6 11 12 22 33 44 66 132 GCF of 20, 81, and 132: 1