Step 1: Divide the number into separate digits:
70984 => 7 0 9 8 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 0 => 7
0 to 9 => 9
9 to 8 => 1
8 to 4 => 4
4 to 7 => 3
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
7 => N
9 => C
1 => C
4 => N
3 => N
Step 4: Combine the filters to a string:
N C C N N = NCCNN