The difference beween a 3-digit number ABC and the number obtained by interchanging it's digits is always divisible by:
The 3-digit number ABC can be written as 100A + 10B + C
Similarly CBA can be written as:
100C + 10B + A
Difference
= (100A + 10B + C) - (100C + 10B + A)
= 100A + 10B + C - 100C - 10B - A
= 99 (A - C)
=9×11(A−C)=3×3×11(A−C)
This number is divisible by only 3 ,9, 11 and 99.