Step 1: Divide the number into separate digits:
64992 => 6 4 9 9 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 4 = 2
4 to 9 = 5
9 to 9 = 0
9 to 2 = 7
2 to 6 = 4
Step 3: Combine the filters to a string:
2 5 0 7 4 = 25074