---
title: "Write a C# program to check a number is prime or not?"  
description: "Write a C# program to check a number is prime or not?"  
author: "Steilla Mitchel"  
published: 2021-11-19  
updated: 2021-11-19  
canonical: https://www.mindstick.com/forum/156855/write-a-c-sharp-program-to-check-a-number-is-prime-or-not  
category: "c#"  
tags: ["c#"]  
reading_time: 2 minutes  

---

# Write a C# program to check a number is prime or not?

Write a C# [program to check](https://www.mindstick.com/forum/157542/write-a-java-program-to-check-if-a-list-of-integers-contains-only-odd-numbers) a number is prime or not?

## Replies

### Reply by Ashutosh Kumar Verma

## Prime Number:

A prime number is a number that divided by self or 1 and no other number can divide that is called a prime number. 1 is not a prime number because there is must be divided by two number that are 1 and that number.

```
Ex-      2,3,5,7,11,13,17… etc.
```

## [Program](https://www.mindstick.com/blog/12337/scaling-up-your-mentorship-program):

```
using System;
public class Program
{
 public static void Main()
 {
 int num,I;
 int temp=0;
 Console.WriteLine(“Enter a number to check whether prime or not);
 num=int.Parse(Console.ReadLine());
  for(i=2;i<=num/2;i++)
  {
   if(num%i==0)
   {
    temp=temp+1;
   }
  }
  if(temp==0)
  {
  Console.WriteLine('is Prime');
  }else
  {
  Console.WriteLine('not prime');
  }
 }
}
```

Output:

```
 Enter a number to check whether prime or not      7
7 is prime
```

**Print all prime number between 1 to 100.**

## Program:

```
using System;
public class Program
{
 public static void Main()
 {
 int num,i,j;
  int temp=0, res;
  for(num=2;num<=100;num++)
  {
  for(i=2;i<=num/2;i++)
  {
   if(num%i==0)
   {
    temp=temp+1;
   }
  }
   if(temp==0)
      {
    Console.Write(' '+num);
   }else
   {
    temp=0;
   }
 }
 }
}
```

## Output:

```
  2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
```

\


---

Original Source: https://www.mindstick.com/forum/156855/write-a-c-sharp-program-to-check-a-number-is-prime-or-not

Copyright © MindStick Software Pvt. Ltd. This Markdown version is provided for developers, AI systems, and offline reading.