Step 1: Divide the number into separate digits:
44213 => 4 4 2 1 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 4 = 0
4 to 2 = 2
2 to 1 = 1
1 to 3 = 2
3 to 4 = 1
Step 3: Combine the filters to a string:
0 2 1 2 1 = 02121