Divisor 24391

Prime Number:
Yes!
Divisibility test:
The "greggwith3G Test"
Test Discovered by:
Matt Parker
Date:
11/11/2024

The "greggwith3G Test" for Divisibility by 24391

To determine if any number is divisible by 24391, apply the "greggwith3G 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 31 and subtract this from R.
  3. Take that result and cross off its final digit (units). Take this new number and subtract 2439 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 24391. That is, your original number is divisible by 24391 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 24391-times tables, it should be easy to visually see if Y is divisible by 24391. If the Y is still much larger than 24391, the above process can be repeated until it does reduce to within small multiples of 24391.

Easy!