public static void Main()
Console.Write("Please enter the same number: ");
while (!int.TryParse(Console.ReadLine(), out number) || number < 1000 || number > 9999) Console.WriteLine("Invalid number!!!");
string strNumber = Convert.ToString(number);
ReversedDigit(strNumber);
string exchangedLasWithFirst = strNumber[3] + "" + strNumber[0] + strNumber[1] + strNumber[2];
Console.WriteLine("Last digit in front: {0}", exchangedLasWithFirst);
string exchangedSecondWithThird = strNumber[0] + "" + strNumber[2] + strNumber[1] + strNumber[3];
Console.WriteLine("Exchanged second with third: {0}", exchangedSecondWithThird);
private static void ReversedDigit(string strNumber)
for (int i = strNumber.Length - 1; i >= 0; i--)
if (i == strNumber.Length - 1)
result += strNumber[i] - 48;
result = (result*10) + ((strNumber[i] - 48));
Console.WriteLine("Reversed digit is: {0}", result);
private static void SumOfDigits(string strNumber)
for (int i = 0; i < strNumber.Length; i++)
result += strNumber[i] - 48;
Console.WriteLine("The sum of digits is: {0}", result);