-15
The lowest whole number that goes into 35, 81, and 15 is one. There is no larger number.
It does not, the mass number of nitrogen is 14 not 15.
1, 3, 5, 15.
1, 2, 7, 14
1, 2, 7, 14.
1, 2, 7, 14.
The number 5 is common to both 15 and 100.
2 and 7
7
2
1