Step 1: Divide the number into separate digits:
61890 => 6 1 8 9 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 1 = 5
1 to 8 = 7
8 to 9 = 1
9 to 0 = 9
0 to 6 = 6
Step 3: Combine the filters to a string:
5 7 1 9 6 = 57196