You can do this in many ways:
int i = 123893232;
Console.WriteLine(i.ToString());//123893232
Console.WriteLine(Convert.ToString(i));//123893232
Console.WriteLine(String.Format("{0:C}", i));//123 893 232,00 zł(Polish)
Console.WriteLine(String.Format("{0:D}", i));//123893232
Console.WriteLine(String.Format("{0:E}", i));//1,238932E+008
Console.WriteLine(String.Format("{0:F}", i));//123893232,00
Console.WriteLine(String.Format("{0:G}", i));//123893232
Console.WriteLine(String.Format("{0:N}", i));//123 893 232,00
Console.WriteLine(String.Format("{0:P}", i));//12 389 323 200,00
Console.WriteLine(String.Format("{0:X}", i));//76275F0