Step 1: Divide the number into separate digits:
44396 => 4 4 3 9 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 4 => 0
4 to 3 => 1
3 to 9 => 6
9 to 6 => 3
6 to 4 => 2
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
0 => E
1 => C
6 => N
3 => N
2 => N
Step 4: Combine the filters to a string:
E C N N N = ECNNN