What does it mean to say that b is a divisor of a?
Assuming b is non-zero.
— It means b is a factor of a,
— It means a/b is an Integer number.
We say b divides a, if a = mb for some m.
Where a, b, and m are integers.
Number a is completely divisible by b, there wouldn’t be a reminder on division.
For example:
Lets say a = 8, and b = 2.
8 is completely divisible by 2.
So, 2 is one of the divisors of 8.
Positive divisors of 8 are 1,2,4,8.