Divisor 28007

To determine if any number is divisible by 28007, you must apply 2 tests successively. If all of them 'pass' - that is, if your number is divisible by 7 and 4001 - then it is divisible by 28007.

The following tests must pass:

• Test if a number is divisible by 7
• The "Jacob Melcher Test" for Divisibility by 4001

Easy!