The number one.
5 goes into 155 evenly. 155/5 = 31
One.
One.
7 and 31 go into 217 evenly.
Only 1 & 31... 31 is a prime number !
1 and 5.
1 and 3.
9.
1, 3, 5, 9, 15, 45.
Only the number one (1) goes into both 100 and 31 evenly.
1, 3, 5, 9, 15, 45.
9