SoftUni - 5.6 Four-Digit Number

//Write a program that takes as input a four-digit number in format abcd (e.g. 2011) and performs the following:
Calculates the sum of the digits (in our example 2+0+1+1 = 4).
Prints on the console the number in reversed order: dcba (in our example 1102).
Puts the last digit in the first position: dabc (in our example 1201).
Exchanges the second and the third digits: acbd (in our example 2101).
The number has always exactly 4 digits and cannot start with 0.

using System;

class FourDigit
{
    static void Main()
    {
        Console.Write("Enter four-digit number = ");
        string numberA = Console.ReadLine();
        int fourDigits = int.Parse(numberA);

        int d = fourDigits % 10;
        int c = ((fourDigits / 10) % 10);
        int b = ((fourDigits / 100) % 10);
        int a = ((fourDigits / 1000) % 10);

        Console.WriteLine("Sum of digits: {0}", a + b + c + d);
        Console.WriteLine("Reversed digits: {0}{1}{2}{3}", d, c, b, a);
        Console.WriteLine("Last digit in front: {0}{1}{2}{3}", d, a, b, c);
        Console.WriteLine("Second and third digits exchanged: {0}{1}{2}{3}", a, c, b, d);
    }
}