Here are some programs for the ICSE computer application students. They are number programs. These programs are very important because they can be asked in the ICSE boards as it is or with a little twist or in combination with other programs.

**Prime Number:**A prime number is a number that is divisible only by two numbers one and itself(For example 5 , it is divisible only by 1 and itself)

import java.io.*;

class prime_number

{

public static void main()throws IOException

{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

System.out.println(“Give a number”);

int num=Integer.parseInt(br.readLine());

int count=0;

for(int i=1;i<=num;i++)

{

if(num%i==0)

count++;

}

if(count==2)

{

System.out.println(“This is a prime number”);

}

else

{

System.out.println(“This is not a prime number”);

}

}

}

I/P:- 5

O/P: This is a primenumber

I/P:- 12

O/P: This is not a prime number

2.** Perfect Number:** A perfect number is a number whose factor’s(excluding the number

)sum is equal to the number(for example 6 has three factors 1, 2 and 3 and their sum is 6)

import java.io.*;

class perfect_number

{

public static void main()throws IOException

{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

System.out.println(“Give a number”);

int num=Integer.parseInt(br.readLine());

int sum=0;

{

for(int i=1;i<num;i++)

{

if(num%i==0)

sum+=i;

}

if(sum==num)

{

System.out.println(“This is a perfect number”);

}

else

{

System.out.println(“This is not a perfect number”);

}

}

}

}

I/P:- 6

O/P: This is a perfectnumber

I/P:- 12

O/P: This is not a perfect number

3. **Special number:**A special number is a number whose digits factorial’s sum is equivalent to the number(For example 145:- 1|+4|+5|=1+24+120=145). In this program a special() function is made to do the task, the function is called from main function by making an object of the class.

import java. io. *;

class specialno

{

public void special(int num)

{

int n=num;int sum=0;

while(num!=0)

{

int pro=1;

int rem=num%10;

num=num/10;

for(int i=1;i<=rem;i++)

pro*=i;

sum+=pro;

}

if(sum==n)

System.out.println(“This is a special number”);

else

System.out.println(“This is not a special number”);

}

public static void main()throws IOException

{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

System.out.println(“Please enter a number to check”);

int num=Integer.parseInt(br.readLine());

specialno obj=new specialno();

obj.special(num);

}

}

I/P:- 145

O/P: This is a special number

I/P:- 12

O/P: This is not a special number