11.
Factorial of a Number
import java.util.Scanner;
class Factorial {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
int fact = 1;
for (int i = 1; i <= n; i++) {
fact *= i;
System.out.println("Factorial = " + fact);
VDT:
Variable Data Type Description
n int Input number
fact int Factorial result
i int Loop counter
12. Reverse of a Number
import java.util.Scanner;
class ReverseNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
int rev = 0;
for (int i = n; i > 0; i = i / 10) {
int d = i % 10;
rev = rev * 10 + d;
System.out.println("Reversed Number = " + rev);
VDT:
Variable Data Type Description
n int Input number
rev int Reversed number
i int Loop variable
d int Digit extracted
13. Sum of Digits
import java.util.Scanner;
class SumDigits {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
int sum = 0;
for (int i = n; i > 0; i = i / 10) {
int d = i % 10;
sum += d;
System.out.println("Sum of digits = " + sum);
VDT:
Variable Data Type Description
n int Input number
sum int Sum of digits
i int Loop variable
d int Extracted digit
14. Armstrong Number (153 = 1³+5³+3³)
import java.util.Scanner;
class Armstrong {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
int sum = 0, temp = n;
for (int i = n; i > 0; i = i / 10) {
int d = i % 10;
sum += d * d * d;
if (sum == temp)
System.out.println(n + " is an Armstrong number.");
else
System.out.println(n + " is NOT an Armstrong number.");
VDT:
Variable Data Type Description
n int Input number
sum int Sum of cubes of digits
temp int Copy of original number
i int Loop variable
d int Extracted digit
15. Prime Number Check
import java.util.Scanner;
class PrimeCheck {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
int count = 0;
for (int i = 1; i <= n; i++) {
if (n % i == 0) count++;
if (count == 2)
System.out.println(n + " is Prime.");
else
System.out.println(n + " is NOT Prime.");
VDT:
Variable Data Type Description
n int Input number
count int Counts number of divisors
i int Loop counter
16. Multiplication Table
import java.util.Scanner;
class Table {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
for (int i = 1; i <= 10; i++) {
System.out.println(n + " x " + i + " = " + (n * i));
VDT:
Variable Data Type Description
n int Input number
i int Loop counter
17. Even Numbers up to N
import java.util.Scanner;
class EvenNumbers {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter limit: ");
int n = sc.nextInt();
for (int i = 2; i <= n; i += 2) {
System.out.print(i + " ");
VDT:
Variable Data Type Description
n int Upper limit
i int Loop counter
18. Odd Numbers up to N
import java.util.Scanner;
class OddNumbers {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter limit: ");
int n = sc.nextInt();
for (int i = 1; i <= n; i += 2) {
System.out.print(i + " ");
VDT:
Variable Data Type Description
n int Upper limit
i int Loop counter
19. Sum of Even Digits of a Number
import java.util.Scanner;
class SumEvenDigits {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
int sum = 0;
for (int i = n; i > 0; i = i / 10) {
int d = i % 10;
if (d % 2 == 0)
sum += d;
System.out.println("Sum of even digits = " + sum);
}
}
VDT:
Variable Data Type Description
n int Input number
sum int Sum of even digits
i int Loop variable
d int Extracted digit
20. Greatest of Two Numbers
import java.util.Scanner;
class GreatestTwo {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter first number: ");
int a = sc.nextInt();
System.out.print("Enter second number: ");
int b = sc.nextInt();
if (a > b)
System.out.println("Greatest = " + a);
else
System.out.println("Greatest = " + b);
VDT:
Variable Data Type Description
a int First number
b int Second number
21: Neon Number
Definition:
A number is called a Neon Number if the sum of digits of its square is equal to the
number itself.
Example: 9 → 9² = 81 → 8 + 1 = 9 (Neon Number)
import java.util.Scanner;
class NeonNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n, sq, sum = 0, d;
System.out.print("Enter a number: ");
n = sc.nextInt();
sq = n * n;
for(; sq > 0; sq = sq / 10) {
d = sq % 10;
sum = sum + d;
if(sum == n)
System.out.println(n + " is a Neon Number.");
else
System.out.println(n + " is not a Neon Number.");
VDT
Variable Data Type Description
n int Input number
sq int Square of the number
sum int Sum of digits of square
d int Extracted digit
22: Armstrong Number
Definition:
A number is called an Armstrong Number if the sum of cubes of its digits is equal to
the number itself.
Example: 153 → 1³ + 5³ + 3³ = 153 (Armstrong Number)
import java.util.Scanner;
class Armstrong {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n, temp, d, sum = 0;
System.out.print("Enter a number: ");
n = sc.nextInt();
temp = n;
for(; n > 0; n = n / 10) {
d = n % 10;
sum = sum + (d * d * d);
if(sum == temp)
System.out.println(temp + " is an Armstrong Number.");
else
System.out.println(temp + " is not an Armstrong Number.");
VDT
Variable Data Type Description
n int Input number
temp int Copy of number
d int Extracted digit
sum int Sum of cubes of digits
23: Strong Number
Definition:
A number is called a Strong Number if the sum of factorials of its digits is equal to the
number itself.
Example: 145 → 1! + 4! + 5! = 145 (Strong Number)
import java.util.Scanner;
class StrongNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n, temp, d, fact, i, sum = 0;
System.out.print("Enter a number: ");
n = sc.nextInt();
temp = n;
for(; n > 0; n = n / 10) {
d = n % 10;
fact = 1;
for(i = 1; i <= d; i++) {
fact = fact * i;
sum = sum + fact;
if(sum == temp)
System.out.println(temp + " is a Strong Number.");
else
System.out.println(temp + " is not a Strong Number.");
}
VDT
Variable Data Type Description
n int Input number
temp int Copy of number
d int Extracted digit
fact int Factorial of digit
i int Loop counter
sum int Sum of factorials
24: Harshad Number
Definition:
A number is called a Harshad Number (or Niven Number) if it is divisible by the sum of
its digits.
Example: 18 → (1 + 8) = 9 → 18 ÷ 9 = 2 (Harshad Number)
import java.util.Scanner;
class Harshad {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n, temp, d, sum = 0;
System.out.print("Enter a number: ");
n = sc.nextInt();
temp = n;
for(; n > 0; n = n / 10) {
d = n % 10;
sum = sum + d;
if(temp % sum == 0)
System.out.println(temp + " is a Harshad Number.");
else
System.out.println(temp + " is not a Harshad Number.");
}
VDT
Variable Data Type Description
n int Input number
temp int Copy of number
d int Extracted digit
sum int Sum of digits
25: Automorphic Number
Definition:
A number is called an Automorphic Number if its square ends with the number itself.
Example: 25 → 25² = 625 (ends with 25 → Automorphic Number)
import java.util.Scanner;
class Automorphic {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n, sq, digits = 0, div, temp;
System.out.print("Enter a number: ");
n = sc.nextInt();
sq = n * n;
temp = n;
for(; temp > 0; temp = temp / 10) {
digits++;
div = 1;
for(int i = 1; i <= digits; i++) {
div = div * 10;
if(sq % div == n)
System.out.println(n + " is an Automorphic Number.");
else
System.out.println(n + " is not an Automorphic Number.");
VDT
Variable Data Type Description
n int Input number
sq int Square of number
digits int Number of digits
div int Divisor (10^digits)
temp int Copy of number
26: Spy Number
Definition:
A Spy Number is one where the sum of digits = product of digits.
Example: 1124 → Sum = 1+1+2+4 = 8, Product = 1×1×2×4 = 8 → Spy Number
import java.util.Scanner;
class SpyNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n, d, sum = 0, prod = 1;
System.out.print("Enter a number: ");
n = sc.nextInt();
int temp = n;
for(; n > 0; n = n / 10) {
d = n % 10;
sum = sum + d;
prod = prod * d;
}
if(sum == prod)
System.out.println(temp + " is a Spy Number.");
else
System.out.println(temp + " is not a Spy Number.");
VDT
Variable Data Type Description
n int Input number
temp int Copy of number
d int Extracted digit
sum int Sum of digits
prod int Product of digits
27: Kaprekar Number
Definition:
A Kaprekar Number is one where the square of the number can be split into two parts,
and their sum equals the number.
Example: 45 → 45² = 2025 → 20 + 25 = 45 → Kaprekar
import java.util.Scanner;
class KaprekarNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n;
System.out.print("Enter a number: ");
n = sc.nextInt();
int sq = n * n;
int count = 0;
for(int i = sq; i > 0; i = i / 10) {
count++;
int pow = 1;
for(int i = 1; i <= count / 2; i++) {
pow = pow * 10;
int right = sq % pow;
int left = sq / pow;
if(right + left == n)
System.out.println(n + " is a Kaprekar Number.");
else
System.out.println(n + " is not a Kaprekar Number.");
VDT
Variable Data Type Description
n int Input number
sq int Square of number
count int Number of digits in square
pow int Power of 10 divider
right int Right part of square
left int Left part of squar
28: Disarium Number
Definition:
A Disarium Number is one where the sum of its digits powered with their position =
number itself.
Example: 135 → 1¹ + 3² + 5³ = 135 → Disarium
import java.util.Scanner;
class DisariumNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n, d, count = 0;
System.out.print("Enter a number: ");
n = sc.nextInt();
int temp = n;
// count digits
for(int i = n; i > 0; i = i / 10) {
count++;
int sum = 0;
for(int i = n; i > 0; i = i / 10) {
d = i % 10;
int pow = 1;
for(int j = 1; j <= count; j++) { // careful: single loop per stage
pow = pow * d;
sum = sum + pow;
count--;
if(sum == temp)
System.out.println(temp + " is a Disarium Number.");
else
System.out.println(temp + " is not a Disarium Number.");
VDT
Variable Data Type Description
n int Input number
temp int Copy of number
d int Extracted digit
count int Number of digits and position counter
pow int Digit raised to position
sum int Sum of powered digits
29: Duck Number
Definition:
A Duck Number contains zero(s) in it, but not at the beginning.
Example: 507 → Duck Number, but 0123 → Not Duck
import java.util.Scanner;
class DuckNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
String num = sc.next(); // take as string for easy check
if(num.charAt(0) == '0') {
System.out.println(num + " is not a Duck Number.");
} else if(num.contains("0")) {
System.out.println(num + " is a Duck Number.");
} else {
System.out.println(num + " is not a Duck Number.");
VDT
Variable Data Type Description
num String Input number as string
30: Buzz Number
Definition:
A Buzz Number is one which is divisible by 7 or ends with digit 7.
Example: 49 → divisible by 7 → Buzz Number
import java.util.Scanner;
class BuzzNumber {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int n;
System.out.print("Enter a number: ");
n = sc.nextInt();
if(n % 7 == 0 || n % 10 == 7)
System.out.println(n + " is a Buzz Number.");
else
System.out.println(n + " is not a Buzz Number.");
VDT
Variable Data Type Description
n int Input number
