Divisor 15973

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

The "Christopher Mrstik Test" for Divisibility by 15973

To determine if any number is divisible by 15973, apply the "Christopher Mrstik 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 902 and add to R.
  3. Take that result and cross off its final digit (units). Take this new number and add 4792 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 15973. That is, your original number is divisible by 15973 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 15973-times tables, it should be easy to visually see if Y is divisible by 15973. If the Y is still much larger than 15973, the above process can be repeated until it does reduce to within small multiples of 15973.

Easy!