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#region Required project assemblies using System; #endregion namespace IsPrimeNumber { internal class Program { private static bool IsPrimeNumber(int number, out int divisibleBy) { divisibleBy = -1; // Set the out parameter as -1, for those numbers which are prime values. if (number <= 1) { return false; // Return false if the value is less than or equal to one. } for (int i = 2; i <= Math.Sqrt(number); i++) { if (number % i == 0) { divisibleBy = i; // Set the out param as the divisible by value. return false; } } return true; // This means it's a prime number. } private static void Main() { int userChoice; do { Console.Write("Please enter an integer number to see if it's a prime number: "); Int32.TryParse(Console.ReadLine(), out userChoice); Console.WriteLine(); // New line. } while (userChoice <= 0); int numberDivisible; if (IsPrimeNumber(userChoice, out numberDivisible)) { Console.WriteLine("Your number is a prime value."); } else { if (numberDivisible == -1) { Console.WriteLine("Your number is NOT regarded as a prime value."); } else { Console.WriteLine("Your number is NOT a prime value as it's divisible by {0}.", numberDivisible); } } Console.WriteLine(); // New line. Console.WriteLine("Press any key to continue . . ."); Console.ReadKey(true); } } }