Step 1: Divide the number into separate digits:
17826 => 1 7 8 2 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 7 = 6
7 to 8 = 1
8 to 2 = 6
2 to 6 = 4
6 to 1 = 5
Step 3: Combine the filters to a string:
6 1 6 4 5 = 61645