How to find the common multiple and common factor of 39 and 117 fast !1

How to find the common multiple and common factor of 39 and 117 fast !1

39=3*13
117=3*3*13
The common multiple satisfies the multiple of 117
The common factor is 39

Common factor and common multiple of 15,20,36, 13,39,65

The greatest common factor of 15, 20 and 36 is 1, and the least common multiple is 180,
The greatest common factor of 13, 39 and 65 is 13, and the least common multiple is 195

How to quickly calculate the least common multiple and the greatest common factor? For example: 12 and 36

You can see at a glance, with the largest number, remove