Divisor 28021

To determine if any number is divisible by 28021, you must apply 2 tests successively. If all of them 'pass' - that is, if your number is divisible by 7 and 4003 - then it is divisible by 28021.

The following tests must pass:

• Test if a number is divisible by 7
• The "Filip Sowa Test" for Divisibility by 4003

Easy!