Step 1: Divide the number into separate digits:
37693 => 3 7 6 9 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 7 => 4
7 to 6 => 1
6 to 9 => 3
9 to 3 => 6
3 to 3 => 0
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
4 => N
1 => C
3 => N
6 => N
0 => E
Step 4: Combine the filters to a string:
N C N N E = NCNNE