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Special Number in Java

In this section, we will learn what is a special number and also create Java programs to check if the given number is a special number or not. The special number program frequently asked in Java coding tests and academics.

Special Number

If the sum of the factorial of digits of a number (N) is equal to the number itself, the number (N) is called a special number.

Special Number in Java

Let's understand it through an example.

Special Number Example

Consider a number 145 and check it is a special number or not.

The digits of the number are: 1, 4, 5

Factorial of digits:

!1 = 1

!4 = 4*3*2*1 = 24

!5 = 5*4*3*2*1 = 120

Sum of factorial of digits = 1 + 24 + 120 = 145

Compare the sum of the factorial of digits with the given number, i.e. 145 = 145. We observe that both are equal.

Hence, the given number 145 is a special number.

Let's check another number 1034.

The digits of the number are: 1, 0, 3, 4

Factorial of digits:

!1 = 1

!0 = 1

!3 = 3*2*1 = 6

!4 = 4*3*2*1 =24

Sum of factorial of digits = 1 + 1 + 6 + 24 = 32

Compare the sum of the factorial of digits with the given number, i.e. 32 ≠ 1034. We observe that the sum of factorial of digits is not equal to the given number.

Hence, the given number 1034 is not a special number.

Some other special numbers are 2, 40585, etc.

Steps to Find Special Number

  1. Read or initialize a number (N).
  2. Split the given number (N) into digits if the number has more than one digit.
  3. Find the factorial of all digits.
  4. Sum up the factorial and store it in a variable (s).
  5. Compare the sum with the given number (N).
  6. If the sum is equal to the number itself, the number (N) is a special number, else not.

Let's implement the above logic in a Java program.

Special Number Java Program

SpecialNumberExample1.java

Output 1:

Enter a number: 40585
40585 is a special number.

Output 2:

Enter a number: 176
176 is not a special number.

Special Number Within a Range

SpecialNumberExample2.java

Output:

Enter the lower range: 1
Enter the upper range: 100000
1	2	145	40585	





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