Divisor 863

Prime Number:
Yes!

Test for Divisibility by 863

To determine if any number is divisible by 863, apply this 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 108 and subtract this from R.
  3. Take that result and cross off its final digit (units). Take this new number and add 259 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 863. That is, your original number is divisible by 863 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 863-times tables, it should be easy to visually see if Y is divisible by 863. If the Y is still much larger than 863, the above process can be repeated until it does reduce to within small multiples of 863.

Easy!