Divisor 1493

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

The "Carl Test" for Divisibility by 1493

To determine if any number is divisible by 1493, apply the "Carl Test":

  1. If your number ("X") has 6 digits or more, separate the last (smallest) 5 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 6 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 add 448 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 1493. That is, your original number is divisible by 1493 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 1493-times tables, it should be easy to visually see if Y is divisible by 1493. If the Y is still much larger than 1493, the above process can be repeated until it does reduce to within small multiples of 1493.

Easy!