Divisor 1723

To determine if any number is divisible by 1723, apply the "Jonathan 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 L^eft and R^ight (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 66 and add to R.
3. Take that result and cross off its final digit (units). Take this new number and add 517 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 1723. That is, your original number is divisible by 1723 if (and only if) Y is. Now that it's much smaller, with basic knowledge of your 1723-times tables, it should be easy to visually see if Y is divisible by 1723. If the Y is still much larger than 1723, the above process can be repeated until it does reduce to within small multiples of 1723.

Easy!