Step 1: Divide the number into separate digits:
83961 => 8 3 9 6 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 3 => 5
3 to 9 => 6
9 to 6 => 3
6 to 1 => 5
1 to 8 => 7
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
5 => N
6 => N
3 => N
5 => N
7 => N
Step 4: Combine the filters to a string:
N N N N N = NNNNN