Here's a Python program to check whether a given number is an Armstrong number or not:
```python
def is_armstrong_number(num):
# Convert the number to string to count the number of digits
num_str = str(num)
num_digits = len(num_str)
# Calculate the sum of digits raised to the power of the number of digits
armstrong_sum = sum(int(digit)**num_digits for digit in num_str)
# Check if the sum is equal to the original number
if armstrong_sum == num:
return True
else:
return False
# Take input from the user
num = int(input("Enter a number: "))
# Check if the number is an Armstrong number
if is_armstrong_number(num):
print(num, "is an Armstrong number")
else:
print(num, "is not an Armstrong number")
```
In the above program, the function `is_armstrong_number` takes a number as input and checks whether it is an Armstrong number or not. It converts the number to a string to count the number of digits. Then, it calculates the sum of each digit raised to the power of the number of digits. Finally, it compares the sum with the original number and returns `True` or `False` accordingly.
The program prompts the user to enter a number, calls the `is_armstrong_number` function to check if it is an Armstrong number, and prints the appropriate message based on the result.