# Python Code Example: Neon number

This Python code checks if a given number is a neon number. A neon number is a number for which the sum of the digits of its square equals the original number. The program prompts the user to input a number, calculates its square, and then sums the digits of the square. Finally, it compares this sum to the original number and prints whether the number is a neon number or not.

## Code Example

``````# Initialize the sum variable to 0
sum = 0

# Prompt the user to enter a number
print("Enter the number to check:")

# Read the input and convert it to an integer
num = int(input())

# Calculate the square of the number
square = num * num

# Loop to sum the digits of the square
while (square != 0):
# Extract the last digit of the square
digit = square % 10

# Add the digit to the sum
sum = sum + digit

# Remove the last digit from the square
square = square // 10

# Check if the original number is equal to the sum of the digits of its square
if (num == sum):
# If true, print that the number is a neon number
print(str(num) + " is a neon number.")
else:
# If false, print that the number is not a neon number
print(str(num) + " is not a neon number.")
``````

### Output

``````Enter a number to check for neon number:
9
9 is a neon number.

Enter a number to check for neon number:
30
30 is not a neon number.``````

### Code Explanation

#### Initialize Variables and Input

``````sum = 0
print("Enter the number to check:")
num = int(input())
square = num * num``````
1. Initialize `sum`: `sum = 0` initializes a variable `sum` to 0. This variable will be used to store the sum of the digits of the square of the number.
2. Prompt for Input: `print("Enter the number to check:")` prints a message asking the user to enter a number.
3. Read Input: `num = int(input())` reads the user input, converts it to an integer, and assigns it to the variable `num`.
4. Calculate Square: `square = num * num` calculates the square of `num` and assigns the result to the variable `square`.

#### Sum the Digits of the Square

``````while (square != 0):
digit = square % 10
sum = sum + digit
square = square // 10``````
1. While Loop: `while (square != 0):` initiates a loop that continues as long as `square` is not equal to 0. This loop extracts and sums the digits of `square`.
2. Extract Last Digit: `digit = square % 10` extracts the last digit of `square` by taking the remainder of `square` divided by 10. This digit is stored in `digit`.
3. Add Digit to Sum: `sum = sum + digit` adds the extracted digit `digit` to the variable `sum`.
4. Remove Last Digit: `square = square // 10` removes the last digit from `square` by performing integer division by 10. This effectively shifts all digits of `square` one place to the right.

#### Check for Neon Number

``````if (num == sum):
print(str(num) + " is a neon number.")
else:
print(str(num) + " is not a neon number.")``````
1. Comparison: `if (num == sum):` checks if the original number `num` is equal to the sum of the digits of its square.
2. Print Result:
• If `num` is equal to `sum`, the code executes `print(str(num) + " is a neon number.")`, printing that `num` is a neon number.
• If `num` is not equal to `sum`, the code executes `print(str(num) + " is not a neon number.")`, printing that `num` is not a neon number.