This solution for easy LC problem is very concise the easy to understand don’t you think?

```
class Solution {
val isPrime: (Int) -> Boolean = { num ->
!(2..num/2).any { num % it == 0 }
}
fun countPrimeSetBits(L: Int, R: Int): Int {
var sum = 0
for(i in L..R){
val candidate = Integer.bitCount(i)
sum += if(candidate > 1 && isPrime(candidate)) 1 else 0
}
return sum
}
}
```

```
Runtime: 204 ms, faster than 20.00% of Kotlin online submissions for Prime Number of Set Bits in Binary Representation.
Memory Usage: 32.7 MB, less than 100.00% of Kotlin online submissions for Prime Number of Set Bits in Binary Representation.
```

We loop through from L to R (inclusive) and for each number, we count the number of set bits using `Integer.bitCount()`

and then we check if the number of bits is a prime number.