A cyclic number with digits has a very interesting property:
When it is multiplied by , all the products have exactly the same digits, in the same order, but rotated in a circular fashion!
The smallest cyclic number is the -digit number :
The next cyclic number is with digits :
Note that for cyclic numbers, leading zeros are important.
There is only one cyclic number for which, the eleven leftmost digits are and the five rightmost digits are (i.e., it has the form with an unknown number of digits in the middle). Find the sum of all its digits.
Write-up coming later
The complete problem is available here. An approach, code, and answer will be added later.