Program to find prime number

In this post, you will learn programs in different languages to print Prime numbers.

A prime number is a whole number greater than 1, whose only factors are 1 and itself, like -2, 3, 5, 7, 11 etc. For example, 17 is a prime number because it is only divisible by 1 and 17, on the other hand, 18 is not a prime number because it is divisible by 2, 3, 6, 9 and number itself.

Java print prime numbers from 1 to 20 using for loop

Here, we have used for loop to get prime numbers from 1 to 20. We loop over the number range (1 to 20) and check whether the number is prime or not. The for loop iterates from i=0 to i=given number, if the remainder of i/num = 0 then increases the count by 1. After all the iterations, if counter=2, then that number is a prime number.

public class CheckPrimeNumbers
{
    public static void main (String[] args)
    {		
       int i =0;
       int num =0;
       
       String  prime_numbers = "";

       for (i = 1; i <= 20; i++)         
       { 		  	  
          int counter=0; 	  
          for(num =i; num>=1; num--)
    	  {
             if(i%num==0)
    	     {
     		    counter = counter + 1;
    	     }
    	  }
    	  if (counter ==2)
    	  {
    	     prime_numbers = prime_numbers + i + " ";
    	  }	
       }	
       System.out.println("Prime Numbers between 1 and 20 :");
       System.out.println(prime_numbers);
    }
}

Output of the above code:

Prime Numbers between 1 and 20 :
2 3 5 7 11 13 17 19

PHP Prime Number Program using While Loop

The following PHP code prints a list of prime numbers between 1 and 100 (that is, numbers not divisible by something other than 1 or the number itself) using a while loop.

<?php  
	$limit = 30;
	$init = 2;
	
	while(TRUE)
	{
		$div = 2;
		if($init > $limit) 
		{
			break;
		}
		while(TRUE)
		{
			if($div > sqrt($init))
			{
				echo $init."  ";
				break;
			}
			if($init % $div == 0) 
			{
				break;
			}
			$div = $div + 1;
		}
		$init = $init + 1;
	}
?>

Output of the above code:

2  3  5  7  11  13  17  19  23  29

Python Program to print Prime Numbers between interval

Here is the Python program to print prime numbers between given interval using for loop. Numbers less than or equal to 1 are not prime numbers. That's why, we have started the range from 1.

for num in range(1, 50):  
   if num > 1:  
       for i in range(2,num):  
           if (num % i) == 0:  
               break  
       else:  
           print(num)

Output of the above code:

C++ program to print Prime Number

The given C++ program takes the range and finds all the prime numbers between the range and also prints the number of prime numbers.

#include<iostream>
using namespace std;

//function to check for prime number
void prime(int num)
{
    int div=0;
    
    //checking for number of divisor
    for(int i=1;i<=num;i++)
    {
       if(num%i==0)
          div++;                
    }
    
    if(div==2)
      cout<<num<<endl;
}
int main()
{
    cout<<"Please enter range: ";    
    int min, max;
    
    cin>>min>>max;
    cout<<"Prime numbers between "<<min<<" and "<<max<<" are:"<<endl;
    
    //finding prime numbers in the given range
    for(int i=min;i<=max;i++)
            prime(i);
    return 0;
}

Output of the above code:

Please enter range: 20 40
Prime numbers between 20 and 40 are:
23
29
31
37

C Program to Find Prime Numbers in a given Range

The given C program takes the range and finds all the prime numbers between the range and also prints the number of prime numbers.

#include <stdio.h>

int main() {
   int min, max, i, flag;
   printf("Please enter range: ");
   scanf("%d %d", &min, &max);
   printf("Prime numbers between %d and %d are: ", min, max);

   // iteration until low is not equal to high
   while (min < max) {
      flag = 0;

      // ignore numbers less than 2
      if (min <= 1) {
         ++min;
         continue;
      }

      // if low is a non-prime number, flag will be 1
      for (i = 2; i <= min / 2; ++i) {
         if (min % i == 0) {
            flag = 1;
            break;
         }
      }

      if (flag == 0)
         printf("%d ", min);

      ++min;
   }
   return 0;
}

Output of the above code:

Please enter range: 50 70
Prime numbers between 50 and 70 are: 53 59 61 67

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