Divisor 173

Prime Number:
Yes!

Test for Divisibility by 173

To determine if any number is divisible by 173, 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 6 and add to R.
  3. Take that result and cross off its final digit (units). Take this new number and add 52 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 173. That is, your original number is divisible by 173 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 173-times tables, it should be easy to visually see if Y is divisible by 173. If the Y is still much larger than 173, the above process can be repeated until it does reduce to within small multiples of 173.

Easy!