Only the number one.
Only the number 1 goes into both 43 & 123... because 43 is a prime number.
The following numbers (factors) divide evenly into 123: 1, 3, 41, 123.
1, 3, 43, 129.
1, 2, 3, 6, 41, 82, 123, 246.
123
Not evenly. 16 goes into 690 43 times with a remainder of 0.125
9 goes into 43 4 times but not evenly
Each of these numbers goes evenly into 86: 1, 2, 43, 86.
114
39, 41 and 43. or 123/3 -2, 123/3 and 123/3 +2
1, 43
Because 3 divides evenly into 123 with no remainder.