Divisor 18991

To determine if any number is divisible by 18991, you must apply 2 tests successively. If all of them 'pass' - that is, if your number is divisible by 7 and 2713 - then it is divisible by 18991.

The following tests must pass:

• Test if a number is divisible by 7
• The "Joseph Dance Test" for Divisibility by 2713

Easy!