Python program to determine whether the given number is a Harshad Number

A Harshad Number (also known as a Niven number) is a positive integer that is divisible by the sum of its digits. For example, 12 is a Harshad number because 12 ÷ (1 + 2) = 12 ÷ 3 = 4, which is a whole number.

Basic Approach

To check if a number is a Harshad number, we need to ?

1. Calculate the sum of all digits in the number
2. Check if the original number is divisible by this sum

Example

my_num = 134
remaining = sum_val = 0

print("Checking if", my_num, "is a Harshad number...")
my_num_copy = my_num

# Calculate sum of digits
while my_num > 0:
    remaining = my_num % 10
    sum_val = sum_val + remaining
    my_num = my_num // 10

print("Sum of digits:", sum_val)

# Check if divisible by sum of digits
if my_num_copy % sum_val == 0:
    print(my_num_copy, "is a Harshad number")
else:
    print(my_num_copy, "isn't a Harshad number")

The output of the above code is ?

Checking if 134 is a Harshad number...
Sum of digits: 8
134 isn't a Harshad number

Testing with a Harshad Number

Let's test with 12, which should be a Harshad number ?

my_num = 12
remaining = sum_val = 0

print("Checking if", my_num, "is a Harshad number...")
my_num_copy = my_num

# Calculate sum of digits
while my_num > 0:
    remaining = my_num % 10
    sum_val = sum_val + remaining
    my_num = my_num // 10

print("Sum of digits:", sum_val)

# Check if divisible by sum of digits
if my_num_copy % sum_val == 0:
    print(my_num_copy, "is a Harshad number")
else:
    print(my_num_copy, "isn't a Harshad number")

The output of the above code is ?

Checking if 12 is a Harshad number...
Sum of digits: 3
12 is a Harshad number

How It Works

• Extract digits: Use my_num % 10 to get the last digit and my_num // 10 to remove it
• Sum calculation: Add each extracted digit to sum_val
• Divisibility check: Use modulus operator to check if original_number % digit_sum == 0

Alternative Approach Using String Conversion

A simpler method using string operations ?

def is_harshad(num):
    digit_sum = sum(int(digit) for digit in str(num))
    return num % digit_sum == 0

# Test with multiple numbers
test_numbers = [12, 18, 19, 21, 134]

for num in test_numbers:
    if is_harshad(num):
        print(f"{num} is a Harshad number")
    else:
        print(f"{num} is not a Harshad number")

The output of the above code is ?

12 is a Harshad number
18 is a Harshad number
19 is not a Harshad number
21 is a Harshad number
134 is not a Harshad number

Conclusion

A Harshad number is divisible by the sum of its digits. You can check this using either a while loop to extract digits or string conversion for a more concise solution. Both approaches effectively determine if a number qualifies as a Harshad number.