Find the missing number
56784 = 4
11111 = 0
72348 = 3
88652 = 5
88811 = 6
75213 = 0
65465 = 3
62257 = ?
I found this quiz in an archive of our company's internal blog. There is no solution provided, nor is there a hint who the author might be. I could not find a solution myself and I am not sure if there is a solution at all.
What I tried (and does not work):
Multiplying every digit with a factor in the range from -18 to 18 and then take the sum. I did this programmatically, trying out all ~70m combinations.
