Divisor 11329

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

The "Erfa Test" for Divisibility by 11329

To determine if any number is divisible by 11329, apply the "Erfa 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 Left and Right (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 499 and add to R.
  3. Take that result and cross off its final digit (units). Take this new number and add 1133 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 11329. That is, your original number is divisible by 11329 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 11329-times tables, it should be easy to visually see if Y is divisible by 11329. If the Y is still much larger than 11329, the above process can be repeated until it does reduce to within small multiples of 11329.

Easy!