Divisor 21959

To determine if any number is divisible by 21959, you must apply 2 tests successively. If all of them 'pass' - that is, if your number is divisible by 7 and 3137 - then it is divisible by 21959.

The following tests must pass:

• Test if a number is divisible by 7
• The "Natalie Gerratt Test" for Divisibility by 3137

Easy!