Divisor 18757

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

The "Ryan McVeety Test" for Divisibility by 18757

To determine if any number is divisible by 18757, apply the "Ryan McVeety Test":

  1. If your number ("X") has 8 digits or more, separate the last (smallest) 7 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 8 digits, L = 0 and therefore R = X.
  2. Multiply L by 2519 and add to R.
  3. Take that result and cross off its final digit (units). Take this new number and subtract 5627 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 18757. That is, your original number is divisible by 18757 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 18757-times tables, it should be easy to visually see if Y is divisible by 18757. If the Y is still much larger than 18757, the above process can be repeated until it does reduce to within small multiples of 18757.

Easy!