A Sphenic number is a product of three distinct prime numbers. For example, 66 is a sphenic number as it is a product of 2, 3, 11 and all these numbers are prime.
Numbers such as 30, 42, 66, 70, 78 etc are all Sphenic Numbers.
Java Program to Check Sphenic Number
import java.util.*;
public class JavaExample
{
//create an array to mark all prime numbers
//up to that range.
static boolean arr[] = new boolean[10000];
static void markPrime()
{
//At the end of the execution of this method, this array
//will contain true for prime numbers and false for non-prime numbers.
//for example: arr[7] will contain true as 7 is prime and arr[10] will be
//false as 10 is not a prime number
Arrays.fill(arr, true);
//iterating array and marking non-prime false
for(int i = 2; i*i < 10000; i++)
{
if(arr[i])
{
for(int j = i*2; j < 10000; j = j+i)
arr[j] = false;
}
}
}
//Checks if the number num is Sphenic or not
static int checkSphenic(int num)
{
int[] divisors = new int[8];
int count = 0;
int j = 0;
for(int i = 1; i <= num; i++)
{
if(num%i == 0 && count < 8)
{
count++;
divisors[j++] = i;
}
}
if(count == 8 && (arr[divisors[0]] && arr[divisors[1]] && arr[divisors[2]]))
return 1;
return 0;
}
public static void main(String args[])
{
markPrime(); //find all prime numbers
Scanner scan = new Scanner(System.in);
System.out.print("Enter a number to check: ");
int num = scan.nextInt();
int isSphenic = checkSphenic(num);
if(isSphenic == 1)
System.out.print("Entered number is Sphenic.");
else
System.out.print("Entered number is not Sphenic.");
}
}
Output 1:
Output 2:
Output 3:
Java Program to print all Sphenic Numbers in a given range
In this example, we are taking input from the user. The program prints all the Sphenic numbers between the entered range by user.
import java.util.*;
public class JavaExample
{
public static void main(String args[])
{
Scanner scan = new Scanner(System.in);
int num,lowerRange,upperRange,temp,count;
System.out.print("Enter the lower range: ");
lowerRange = scan.nextInt();
System.out.print("Enter the upper range: ");
upperRange = scan.nextInt();
for(num = lowerRange; num <= upperRange; num++)
{
int c, f=1;
temp = num;
count=0;
for(int i=2;i<=temp;i++)
{
c=0;
while((temp%i)==0)
{
temp=temp/i;
c++;
}
if(c==1)
{
f=f*i;
count++;
}
}
if(f==num && count==3)
System.out.print(num+"\t");
}
}
}
Output 1: First 100 Sphenic Numbers
Output 2: First 200 Sphenic Numbers
