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Peterson Number in Java

In this section, we will learn what is Peterson number and how can we check whether a given number is Peterson or not through a Java program.

Peterson Number

A number is said to be Peterson if the sum of factorials of each digit is equal to the sum of the number itself.

Steps to Find Peterson Number

  • Read or initialize a number (n).
  • Find the last digit (d) of the given number.
  • Find the factorial (fact) of the digit.
  • Add the factorial (fact) to a variable
  • Repeat steps 2 to 4 until the given number becomes 0.
  • Compare the sum with n. If both are equal, the given number is Peterson, else not.

Example of Peterson Number

Suppose, we have to check the number (n) 145 is Peterson or not.

Number = 145

145 = !1 + !4 + !5




We observe that the number and the sum of factorials of digits are equal to the number itself. Hence, 145 is a Peterson number.

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

Peterson Number Java Program

In the following program, we have taken an array of factorial to quickly find the factorial. You can use the logic also.

Output 1:

Enter a number to check: 145
The given number is a Peterson number.

Output 2:

Enter a number to check: 773
The given number is not a Peterson number.

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