Let N be the 3 digit number.
Let R be the remainder.
So 573921 – R and 575713 – R will be divisible by N
This means the difference between them is also divisible by N.
Difference = (575713 – R – 573921 + R) is divisible by N
Or 1792 divisible by N
N can be 256 from the answer choices!
Correct Answer: Choice B