Divisor 21073

To determine if any number is divisible by 21073, you must apply 2 tests successively. If all of them 'pass' - that is, if your number is divisible by 13 and 1621 - then it is divisible by 21073.

The following tests must pass:

• Test if a number is divisible by 13
• The "Sean Williams Test" for Divisibility by 1621

Easy!