Divisor 3943

To determine if any number is divisible by 3943, apply the "Wiidix Test":

1. If your number ("X") has 10 digits or more, separate the last (smallest) 9 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 10 digits, L = 0 and therefore R = X.
2. Multiply L by 2 and subtract this from R.
3. Take that result and cross off its final digit (units). Take this new number and add 1183 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 3943. That is, your original number is divisible by 3943 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 3943-times tables, it should be easy to visually see if Y is divisible by 3943. If the Y is still much larger than 3943, the above process can be repeated until it does reduce to within small multiples of 3943.

Easy!