# Print all Multiplicative Primes ≤ N in Java

Hi folks, today we will learn how to Print all **Multiplicative Primes ≤ N in java**.

We can assume you know about prime numbers. If you don’t check this: Java Program To Check A Number Is Prime or Not

So, what are multiplicative primes? If the product of the digits of a prime number is also a prime number then the number is known as a multiplicative prime.

Example:

for N=15,

multiplicative primes are { 2, 3, 5, 7, 13} as we can check on multiplying their digits, they will all result in a prime number.

Please Remember there could be multiple ways to solve a particular problem as per your understanding.

## Multiplicative Primes ≤ N: Java Code

import java.util.Scanner; class Main { //check whether the passed no. is prime or not public static boolean checkPrime(int i) { int a=0; for(int j=2;j<=i;j++) { if(i%j==0) a++; if(a>1) return false; } return true; } //calculating the product of digits public static int proDigits(int i) { int a=1; while(i!=0) { a=a*(i%10); i/=10; } return a; } public static void main(String []args) { Scanner sc=new Scanner(System.in); int n=sc.nextInt(); if(n<=1) //Error handler { System.out.println("No Multiplicative prime!"); return; } for(int i=2;i<=n;i++) { if(checkPrime(i)) { int j=proDigits(i); if(checkPrime(j) && j>1) { System.out.print(i+" "); } } } } }

Output:

-5 //input No Multiplicative prime!

20 //input 2 3 5 7 13 17

1 //input No Multiplicative prime!

**Explanation:**

In the above code, we have defined two methods:

**checkprime()**which takes an integer value and will return a**boolean value**based on the decision whether the passed number is prime or not.**proDigits()**which will take an integer number and multiply all the digits of that number and return the result.

So, the program logic is: first, we check whether the number (**up to N) **is prime or not and if the number is prime we will calculate the product of its digits: **k** (say) and again check the whether **k** is prime or not.

Now, you know how to Print all multiplicative primes ≤ N in java.

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