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

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

Last updated:11/19/2021 10:40:50 PM ##### 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:

```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);
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
```