Divisor 4099

Prime Number:
Yes!
Divisibility test:
The "Lawnmower enthusiast Test"
Test Discovered by:
Matt Parker
Date:
11/11/2024

The "Lawnmower enthusiast Test" for Divisibility by 4099

To determine if any number is divisible by 4099, apply the "Lawnmower enthusiast Test":

  1. If your number ("X") has 7 digits or more, separate the last (smallest) 6 digits from the rest. This makes two smaller numbers, call them Left and Right (note: don't add in trailing zeros to L). If there are fewer than 7 digits, L = 0 and therefore R = X.
  2. Multiply L by 156 and subtract this from R.
  3. Take that result and cross off its final digit (units). Take this new number and add 410 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 4099. That is, your original number is divisible by 4099 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 4099-times tables, it should be easy to visually see if Y is divisible by 4099. If the Y is still much larger than 4099, the above process can be repeated until it does reduce to within small multiples of 4099.

Easy!