Armstrong Number in Python

Introduction to Armstrong Number in Python

A number is an Armstrong number if it is equal to the sum of its own digits raised to the number of digits’ power. Let us understand Armstrong’s number by taking an example of a number. Let the number be n. Find out the number of digits in the number. Each digit in the number is taken and raised to the power n. All those are added together, and if the sum of all these numbers is equal to the number itself, then the number n is an Armstrong number. If not, the number n is not an Armstrong number.

How to Determine Armstrong Number in Python?

Let us understand the logic on how to determine the Armstrong numbers in python.

1. The input number is read using input().
2. The entered value is checked to determine if it is an integer or not.
3. The entered value is checked to determine if it is greater than zero.
4. Declare a variable and assign it to zero.
5. The remainder of the input number is found out by using the modulus (%) operator, and this gives each digit in the number.
6. The cube of each digit is found and added to the initialized variable in step 4.
7. The resulting number is floor divided by 10.
8. Until the input number is not greater than zero, repeat steps 5,6 and 7.
9. If the input number is equal to the initialized variable, the statement that the number is an Armstrong number is printed.
10. If the input number is not equal to the initialized variable, the statement that the number is not an Armstrong number is printed.

All the single-digit numbers are Armstrong numbers because, in single-digit numbers, the value of a number of digits “n” is one and anything raised to the power of one is the number “n” itself. Consider an example where the number n=6.

6^1 = 6. Hence 6 is an Armstrong number. There are no two-digit Armstrong numbers. Consider an example where the number n=22.

2^2 + 2^2
=4 + 4
=8

In the above example, the number n=22 is not equal to the sum of its own digits raised to the number of digits’ power. Hence n is not an Armstrong number. There are four three-digit Armstrong numbers. Consider an example where the number n=371.

3^3 + 7^3 + 1^3
=27 + 343 + 1
=371

In the above example, the number n=371 is equal to the sum of its own digits raised to the number of digits’ power. Hence n is an Armstrong number. There are two four-digit Armstrong numbers. Consider an example where the number n=1634.

1^4 + 6^4 + 3^4 + 4^4
=1 + 1296 + 81 + 256
=1634

In the above example, the number n=1634 is equal to the sum of its own digits raised to the number of digits’ power. Hence n is an Armstrong number.

Examples to determine Armstrong Number in Python

Let us see some examples to determine Armstrong number in python, which are given below:

Example #1

Let us understand how to determine Armstrong’s number in a python programming language using the if-else statement.

Code:

# input is taken from the user
number = int(input("Please input a number "))
# Variable result is initialized
result = 0
# cube of each digit is added to find the sum
temporary = number
while temporary > 0:
	  digit = temporary % 10
	  result += digit ** 3
	  temporary //= 10
# result is displayed
if number == result:
	  print(number," - an Armstrong number")
else:
	  print(number," - not an Armstrong number")

Output:

The output of the above program with input as 1234,

Example #2

Let us understand how to determine Armstrong’s number in the python programming language using a list.

Code:

# Program to check Armstrong numbers using list	
number=int(input("Please input any number: "))
number1=list(map(int,str(number)))
number2=list(map(lambda x:x**3,number1))
if(sum(number2)==number):
	print("The given number is an armstrong number. ")
else:
	print("The given number isn't an arsmtrong number. ")

Output:

The output of the above program with input as 542,

Example #3

Let us understand how to determine Armstrong’s number in a python programming language using a recursive function.

Code:

# Program to check Armstrong numbers using recursive function	
# getSum() recursive function is defined
def getSum(number):
    if number == 0:
        return number
    else:
        return pow((number%10),order1) + getSum(number//10)	
# storing the input in number variable
number = int(input("Please input any number: "))	
# len() and str() function is used to find the order
order1 = len(str(number)) 	
# getSum() gives the sum and the sum variable is initialised
sum = getSum(number)	
# the sum is equal to number or not is checked
if sum == int(number):
# Determining if the number is an Armstrong number 
	print(number," - an Armstrong Number.") 
else:
# Determining if the number is not an Armstrong number
	print(number," - not an Armstrong Number.")

Output:

The output of the above program with input as 1634,

Conclusion

In this article, we have learned Armstrong numbers in python, logic to determine Armstrong numbers, and various kinds of python programs using if-else statements, recursive functions, for loop, list to check if a given number is an Armstrong number or not. This article will help the readers trace the programs written in python to determine if a given number is an Armstrong number.

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