Why is it summing a long negative integer to zero????

Code Java:

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import java.util.Scanner;
public class Exercise2_6M
{
    public static void main(String[] args)
    {
        // Create a Scanner
        Scanner input = new Scanner(System.in);
 
        // Enter amount
        System.out.print("Enter an integer:");
        int integer = input.nextInt();
 
        // Calculations
        int rinteger = Math. abs (integer);
        int sum = 0;
        int i=0;
 
        //loop through each digit (starting from the least significant) until the end of the number
        while(rinteger / Math.pow(10,i) > 0)
        {
            sum+=getDigit(rinteger,i);
            i++;
        }
 
 
        // Display results
        System.out.println("Sum all digits in " + integer + " is " + sum);
    }
 
    public static int getDigit(int num, int power)
    {
        return (num % (int)Math.pow(10,power+1)) / (int)Math.pow(10,power);
    }
}

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Is this program built to find the sum of the digits? Or to find the sum of the digits up to the number?

Would 123 be... 1+2+3
or
Would 123 be... 1+2+3+4+5...+122+123

As far as i know, when you apply the power function, it crosses the limit of integer. And shows you the result after that.
You must take care of memory sizes provided to different data types.