Recursive Integer Reversal

Consider the following class definition. What is printed when the main method is executed?

public class ReverseNumber {
    public static int reverseNum(int n, int rev) {
        if(n == 0)
            return rev;
        return reverseNum(n / 10, rev * 10 + n % 10);
    }
    public static void main(String[] args) {
        System.out.println(reverseNum(123, 0));
    }
}