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Prime Number Checker

Steilla Mitchel 295 11-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

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1 Answers

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