C# Reverse int in fast ways

i have been looking for a way to reverse an integer and i have found this

while(left>0)
{
  r = left % 10;
  rev = rev * 10 + r;
  left = left / 10;
}

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but the problem is this code is extremely slow. because it will only be a very small part of big operation.
so i tried to code it myself and i have been to this

string[] userinput = Console.ReadLine().Split(' ');
			int i = int.Parse(userinput[0]);
			int j = int.Parse(userinput[1]);
			int k = int.Parse(userinput[2]);
			int Reverse = 0;
			char[] temp;
			string trans = i.ToString();
			temp = trans.ToCharArray();
			temp.Reverse();
			trans = new string(temp);
			Reverse = int.Parse(trans);
			Console.WriteLine(Reverse);

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but it always gives the value 0 "about the j and k forget about them its just for the rest of my code" so can anyone help me how can i make it work and if this can't be done any new ways to how to make it in quicker way than the shown above because it's really extremely slow.