# Exactly 3 Divisors

Sun Feb 06 2022 02:04:54 GMT+0000 (Coordinated Universal Time)

```import java.io.*;
import java.util.*;

class Solution
{
public static boolean isPrime(int num)
{
if(num==1) return false;
if(num==2 || num==3) return true;
if(num%2==0 || num%3==0) return false;
for(int i=5; i*i<=num; i+=6)
{
if(num%i==0 || num%(i+2)==0)
return false;
}
return true;
}

public static int exactly3Divisors(int N)
{
int count = 0;
for(int i=2; i*i<=N; i++)
{
if(isPrime(i))
count++;
}
return count;
}
}

class Main {
public static void main (String[] args) {
Scanner sc=new Scanner(System.in);

//taking testcases
int T=sc.nextInt();

while(T-->0)
{
Solution obj=new Solution();
int N;
N=sc.nextInt();//taking N
//calling function exactly3Divisors()
System.out.println(obj.exactly3Divisors(N));
}

}
}```
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8. Exactly 3 Divisors Given a positive integer value N. The task is to find how many numbers less than or equal to N have numbers of divisors exactly equal to 3. Example 1: Input: N = 6 Output: 1 Explanation: The only number less than 6 with 3 divisors is 4. Example 2: Input: N = 10 Output: 2 Explanation: 4 and 9 have 3 divisors. Your Task: You don't need to read input or print anything. Your task is to complete the function exactly3Divisors() that takes N as input parameter and returns count of numbers less than or equal to N with exactly 3 divisors. Expected Time Complexity: O(N^1/2 * N^1/4) Expected Auxilliary Space: O(1) Constraints : 1 <= N <= 10^9

https://practice.geeksforgeeks.org/problems/exactly-3-divisors/1/?track=DSASP-Mathematics&batchId=190