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Spy Number in Java

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

Spy Number

A positive integer is called a spy number if the sum and product of its digits are equal. In other words, a number whose sum and product of all digits are equal is called a spy number.

Example of Spy Number

Let's take the number 1124 and check whether the number is a spy or not. First, we will split it into digits (1, 1, 2, 4). After that find the sum and product of all the digits.



We observe that the sum and product of the digits both are equal. Hence, 1124 is a spy number.

Similarly, we can check other numbers also. Some other spy numbers are 22, 123, 132, etc.

Spy Number in Java

Steps to Find Spy Number

  1. Read or initialize a number (n) that you want to check.
  2. Declare two variables sum and product to store sum and product of digits. Initialize sum with 0 and product with 1.
  3. Find the last digit (n%10) of the given number by using the modulo operator.
  4. Add the last digit to the variable sum.
  5. Multiply the last digit with the product variable.
  6. Divide the given number (n) by 10. It removes the last digit.
  7. Repeat steps 3 to 6 until the given number (n) becomes 0.
  8. If the variable sum and product have the same value, then the given number (n) is a spy number, else not a spy number.

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

Spy Number Java Program

Output 1:

Enter the number to check: 123
The given number is a spy number.

Output 2:

Enter the number to check: 456
The given number is a not spy number.


Enter the lower range: 1
Enter upper range: 10000
The Spy numbers between 1 to 10000 are: 
1 2 3 4 5 6 7 8 9 22 123 132 213 231 312 321 1124 1142 1214 1241 1412 1421 2114 2141 2411 4112 4121 4211

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