Divisor 28669

To determine if any number is divisible by 28669, apply this test:

1. If your number ("X") has 9 digits or more, separate the last (smallest) 8 digits from the rest. This makes two smaller numbers, call them L^eft and R^ight (note: don't add in trailing zeros to L). If there are fewer than 9 digits, L = 0 and therefore R = X.
2. Multiply L by 2528 and add to R.
3. Take that result and cross off its final digit (units). Take this new number and add 2867 times the digit you just crossed off. Call this final result "Y".
4. Y will be much smaller than X, but we have preserved divisibility by 28669. That is, your original number is divisible by 28669 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 28669-times tables, it should be easy to visually see if Y is divisible by 28669. If the Y is still much larger than 28669, the above process can be repeated until it does reduce to within small multiples of 28669.

Easy!