Step 1: Divide the number into separate digits:
52646 => 5 2 6 4 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 2 => 3
2 to 6 => 4
6 to 4 => 2
4 to 6 => 2
6 to 5 => 1
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
3 => N
4 => N
2 => N
2 => N
1 => C
Step 4: Combine the filters to a string:
N N N N C = NNNNC