Divisor 20423

To determine if any number is divisible by 20423, you must apply 2 tests successively. If all of them 'pass' - that is, if your number is divisible by 13 and 1571 - then it is divisible by 20423.

The following tests must pass:

• Test if a number is divisible by 13
• The "Adrian I Test" for Divisibility by 1571

Easy!