Check is palindrome in Kotlin

isPalindrome.kt

fun isPalindrome(x: Int): Boolean
{
    if (x < 0) return false
    
    val x = x.toString()
    
    var left = 0;
    var right = x.length - 1;
    
    while (left < right)
    {
        if (x[left] != x[right])
        {
            return false
        }
        
        left++;
        right--;
    }
    
    return true;
}

fun main() {
    println(isPalindrome(0));
    println(isPalindrome(121));
    println(isPalindrome(-121));
    println(isPalindrome(10));
}