Step 1: Divide the number into separate digits:
64369 => 6 4 3 6 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 4 = 2
4 to 3 = 1
3 to 6 = 3
6 to 9 = 3
9 to 6 = 3
Step 3: Combine the filters to a string:
2 1 3 3 3 = 21333