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Prime Number Checker

Steilla Mitchel9411-Jun-2024

Develop a C# function to check whether a given number n is a prime number. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

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Updated on 13-Jun-2024
Steilla Mitchel

Steilla Mitchel

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Ashutosh Kumar Verma

Ashutosh Kumar Verma

13-Jun-2024

Prime Number Checker in C#

Below is a simple implementation of a prime number checker in C#,

Example- 

using System;
class Program
{
   static void Main()
   {
       // Prompt the user to enter a number
       Console.WriteLine("Enter a number to check Prime or not ");
       int number = int.Parse(Console.ReadLine());
       // Check if the entered number is prime or not
       if (IsPrime(number))
       {
           Console.WriteLine(number + " is a prime number.");
       }
       else
       {
           Console.WriteLine(number + " is not a prime number.");
       }
       Console.ReadLine();
   }
   // Function to check if a number is prime
   static bool IsPrime(int number)
   {
       // 0 and 1 are not prime numbers
       if (number < 2)
           return false;
       // Check for divisibility by numbers up to the square root of the number
       for (int i = 2; i <= Math.Sqrt(number); i++)
       {
           if (number % i == 0)
               return false; // If the number is divisible by any number other than 1 and itself, it's not prime
       }
       return true; // If the loop completes without finding any divisors, the number is prime
   }
}

In the above example- 

  • We ask the user to enter a number.
  • We call the IsPrime function to check if the input number is prime.
  • The IsPrime function checks if the number is less than 2 and returns false if it is, because 0 and 1 are not prime numbers.
  • It then checks whether the number is divisible by any of these numbers by iterating from 2 to the square root of the number. If so, the function returns false, indicating that the number is not prime.
  • If the loop completes without finding any divisor, the function returns true, which means the number is prime.

 

Output- 1

Enter a number to check Prime or not
20
20 is not a prime number.

Output- 2

Enter a number to check Prime or not
23
23 is a prime number.

 

This function must carefully check whether the given quantity is prime or not.

 

Also, Read: Fibonacci Sequence

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