A digit in the number is useful if the number is divisible by that digit.

I have been working on this for 2 days now.

Here is what I have:

```
func selfDivide(integer: Int) -> Int {
    var numString = String(integer)
    for character in numString.characters {
        if character % numString == 0 {
            return character
        }
    }
}

```

I'm thinking I have to find a way to use % between that string and character.

The error that I get is:

Binary operator '%' cannot be applied to characters of type 'Character' and 'String'