The greatest common multiple of any set of integers is infinite.
The highest common multiple is infinite, and not very practical. The GCF is 3. The LCM is 84.
The least common multiple is 24.
It is: 240
84
96
84
144
60
The LCM is: 780
The LCM is: 180
420
Least Common Multiple (LCM) for 12 6 is 12.