In this example, you will learn to check whether an n-digit integer is an Armstrong number or not.

To understand this example, you should have the knowledge of the following Python programming topics:

A positive integer is called an Armstrong number of order `n` if

abcd... = a^{n}+ b^{n}+ c^{n}+ d^{n}+ ...

In case of an Armstrong number of 3 digits, the sum of cubes of each digit is equal to the number itself. For example:

153 = 1*1*1 + 5*5*5 + 3*3*3 // 153 is an Armstrong number.

```
# Python program to check if the number is an Armstrong number or not
# take input from the user
num = int(input("Enter a number: "))
# initialize sum
sum = 0
# find the sum of the cube of each digit
temp = num
while temp > 0:
digit = temp % 10
sum += digit ** 3
temp //= 10
# display the result
if num == sum:
print(num,"is an Armstrong number")
else:
print(num,"is not an Armstrong number")
```

**Output 1**

Enter a number: 663 663 is not an Armstrong number

**Output 2**

Enter a number: 407 407 is an Armstrong number

Here, we ask the user for a number and check if it is an Armstrong number.

We need to calculate the sum of the cube of each digit. So, we initialize the sum to 0 and obtain each digit number by using the modulus operator %. The remainder of a number when it is divided by 10 is the last digit of that number. We take the cubes using exponent operator.

Finally, we compare the sum with the original number and conclude that it is Armstrong number if they are equal.

```
num = 1634
# Changed num variable to string,
# and calculated the length (number of digits)
order = len(str(num))
# initialize sum
sum = 0
# find the sum of the cube of each digit
temp = num
while temp > 0:
digit = temp % 10
sum += digit ** order
temp //= 10
# display the result
if num == sum:
print(num,"is an Armstrong number")
else:
print(num,"is not an Armstrong number")
```

You can change the value of `num` in the source code and run again to test it.