prime number, C# - rextester

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Console.Write("Enter a Number : ");
            int num;
            num = Convert.ToInt32(Console.ReadLine());
            int k;
            k = 0;
            for (int i = 1; i <= num/2; i++)
            {
                if (num % i == 0)
                {
                    k++;
                }
            }
            if (k == 2)
            {
                Console.WriteLine("Entered Number is a Prime Number and the Largest Factor is {0}",num);
            }
            else
            {
                Console.WriteLine("Not a Prime Number");
            }
            Console.ReadLine();
        }
    }
}

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Compilation time: 0,14 sec, absolute running time: 10,01 sec, cpu time: 0,08 sec, average memory usage: 24 Mb, average nr of threads: 5, absolute service time: 10,15 sec