# Write a C# Program to check whether a number is prime or not

How to write a C# program to find prime numbers. What is a prime number? And how to find the prime number between two numbers in C#.

**At the very first let’s understand what is a prime number? Then will write the code to find prime number in C#. List of C# programs with examples.**

**What is a prime number?**

A number that is divisible only by itself and 1. Example: (2, 3, 5, 7, 11, 13, 17, 19). One is not a prime number according to the definition a Prime number is divisible with 1 and itself and one doesn’t have exactly two positive divisors.

**C# Program to check whether a number is prime or not **

In this example, We will see how to check whether a number is prime or not in c#. When user will run this code It will ask to enter a number. The output will print the number is prime or not.

using System; namespace CSharpProgram { class Program { static void Main(string[] args) { int num, i, f = 0; Console.Write("Enter any Number: "); num = int.Parse(Console.ReadLine()); for (i = 2; i <= num/2; i++) { if (num % i == 0) { Console.Write("No "+num+" is not a Prime Number"); f = 1; break; } } if (f == 0) { Console.Write("Yes " +num+ " is a Prime Number"); } Console.ReadLine(); } } }

**More examples to find the prime number in C#**

**More examples to find the prime number in C#**

Below, We can see more **C# program to find prime number between two numbers**, for example, find a prime number between 1 to 100 in C#.

**Write a C# program to find Prime Number between 1-100**

using System; namespace CSharpProgram { class Program { static void Main(string[] args) { bool isPrime = true; Console.WriteLine("Prime Numbers between 1 to 100 : "); for (int i = 2; i <= 100; i++) { for (int j = 2; j <= 100; j++) { if (i != j && i % j == 0) { isPrime = false; break; } } if (isPrime) { Console.Write(" " + i); } isPrime = true; } Console.ReadKey(); } } }

**Write a C# program to find Prime Number between n-N.**

using System; namespace CSharpProgram { class Program { static void Main(string[] args) { int n1 = int.Parse(Console.ReadLine()); int n2 = int.Parse(Console.ReadLine()); bool isPrime = true; Console.WriteLine("Prime Numbers between "+n1+" to "+n2+" : "); for (int i = n1; i <= n2; i++) { for (int j = 2; j <= n2; j++) { if (i != j && i % j == 0) { isPrime = false; break; } } if (isPrime) { Console.Write(" " + i); } isPrime = true; } Console.ReadKey(); } } }