CodeEval Prime Palindrome (003)

primepalindrome.cs

using System;
using System.Linq;

namespace Solutions.PrimePalindrome
{
    public class Program
    {
        static void Main(string[] args)
        {
            Console.Write(PrimePalindrome.Solve());
        }
    }

    public class PrimePalindrome
    {
        public static string Solve()
        {
            return Enumerable.Range(1, 1000).Reverse()
                .FirstOrDefault(n => IsPalindrome(n) && IsPrime(n))
                .ToString();
        }

        public static bool IsPalindrome(int n)
        {
            var ns = n.ToString();
            return ns == new String(ns.Reverse().ToArray());
        }

        public static bool IsPrime(int n)
        {
            if ((n & 1) == 0)
                return n == 2;

            for (var i = 3; (i*i) <= n; i += 2)
            {
                if ((n%i) == 0)
                    return false;
            }
            return n != 1;
        }
    }
}