If 8080 = 6, 1357 = 0, 2022 = 1, 1999 = 3 then 6666 = ?

Question

Consider the following pattern:

8809 = 6
7111 = 0
6666 = 4
7652 = 1
3368 = 3
9313 = 1
1008 = 4
9887 = 5
1155 = 0

What is 2021 = ?

Answer 1

8080 = 6 means 6 circles
2022 = 1 means 1 circle
1999 = 3 means 3 circle

so 6666 = 4 means 4 circles