Math puzzles!! can you solve this?

Can you solve this riddle?

If:
8809 = 6
7111 = 0
2172 = 0
6666 = 4
1111 = 0
3213 = 0
7662 = 2
9312 = 1
0000 = 4
2222 = 0
3333 = 0
5555 = 0
8193 = 3
8096 = 5
7777 = 0
9999 = 4
7756 = 1
6855 = 3
9881 = 5
5531 = 0

Then, 2581 = ?

If: 8809 = 6 7111 = 0 2172 = 0 6666 = 4 1111 = 0 3213 = 0 7662 = 2 9312 = 1 0000 = 4 2222 = 0 3333 = 0 5555 = 0 8193 = 3 8096 = 5 7777 = 0 9999 = 4 7756 = 1 6855 = 3 9881 = 5 5531 = 0 Then, 2581 = 2

Answer is '2'

Answer is 2.......

From the above, since 0000 = 4.....so value of 0 = 1

1111 = 0....so value of 1 = 0

2222 = 0....so value of 2 = 0

5555 = 0....so value of 5 = 0

9999 = 4....so value of 9 = 1

8809 = 6.....0 and 9 makes 2.....value of two 8s is 4......so value of 8 = 2

So, value of 2581 = 0 + 0 + 2 + 0 = 2

Anyhow instead of doing this we can take the value of number based on the number of circles in that number......

Second way of doing it..........

In the above series 2581 is the 21st number.......

the difference between 7th and 6th number is 7662 [ 2 ] - 3213 [ 0 ] = 2

the difference between 14th and 13th number is 8096 [ 5 ] - 8193 [ 3 ] = 2

Going with sequence......The difference between 21st and 20th number should be 2

So, 2581 [ X ] - 5531 [ 0 ] = 2. ......So value of  2581 = 2.....

After a long struggle got the answer

Answer is 2