What is the correct datatype for very large numerical values and how is it used?

Question

I am dealing with a question from hackerrank. I am not able to display correct output i don't know which data type to use in this program.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution 
{
    static void Main(String[] args) 
    {
        double n = int.Parse(Console.ReadLine());

        double factorial = 1;
        for (int i = 1; i <= n; i++)
        {
            factorial *= i;
        }

        Console.WriteLine(factorial);
    }
}

I am getting this output

        1.5511210043331E+25

But Expected output is

        15511210043330985984000000

I am thinking to use long but i don't know how. Please suggest me how to deal with it.

Thanks in advance.

Answer 1

As someone suggested in the comments, using BigInteger is also a good idea.

Here is documentation on BigInteger: https://msdn.microsoft.com/en-us/library/system.numerics.biginteger(v=vs.110).aspx

BigInteger Solution:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics; // This is important

class Solution 
{
    static void Main(String[] args) 
    {
        int n = int.Parse(Console.ReadLine()); // No reason to accept a double here

        BigInteger factorial = 1; 

        for (int i = 1; i <= n; i++)
        {
            factorial *= i;
        }

        Console.WriteLine(factorial.ToString());
   }
}