Python: Find the index of the largest prime in the list and the sum of its digits

Last update on March 22 2025 13:47:23 (UTC/GMT +8 hours)

Largest Prime Index and Digit Sum

Write a Python program to find the index of the largest prime in the list and the sum of its digits.

Input:  
[3, 7, 4] 
Output:
[1, 7]

Input:  
[3, 11, 7, 17, 19, 4]
Output:
[4, 10]

Input:  
[23, 17, 201, 14, 10473, 43225, 421, 423, 11, 10, 2022, 342157]
Output:
[6, 7]

Visual Presentation:

Sample Solution:

Python Code:

# License: https://bit.ly/3oLErEI

# Define a function named 'test' that takes a list of numbers as input
def test(nums):
    # Find the maximum prime number in the list along with its index
    n, i = max((n, i) for i, n in enumerate(nums) if is_prime(n))
    
    # Return a list containing the index of the largest prime and the sum of its digits
    return [i, sum(int(c) for c in str(n))]

# Define a function named 'is_prime' that checks if a number is prime
def is_prime(n):
    return n > 1 and all(n % j for j in range(2, int(n ** 0.5) + 1))

# Example 1
nums1 = [3, 7, 4]
print("List of numbers:", nums1)
print("Index of the largest prime in the said list and the sum of its digits:")
print(test(nums1))

# Example 2
nums2 = [3, 11, 7, 17, 19, 4]
print("\nList of numbers:", nums2)
print("Index of the largest prime in the said list and the sum of its digits:")
print(test(nums2))

# Example 3
nums3 = [23, 17, 201, 14, 10473, 43225, 421, 423, 11, 10, 2022, 342157]
print("\nList of numbers:", nums3)
print("Index of the largest prime in the said list and the sum of its digits:")
print(test(nums3))

Sample Output:

List of numbers: [3, 7, 4]
Index of the largest prime in the said list and the sum of its digits:
[1, 7]

List of numbers: [3, 11, 7, 17, 19, 4]
Index of the largest prime in the said list and the sum of its digits:
[4, 10]

List of numbers: [23, 17, 201, 14, 10473, 43225, 421, 423, 11, 10, 2022, 342157]
Index of the largest prime in the said list and the sum of its digits:
[6, 7]

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to iterate over a list, find all prime numbers, and return the index of the largest prime along with the sum of its digits.
• Write a Python program to use a helper function to test for prime numbers and then select the largest prime's index and digit sum.
• Write a Python program to compute the digit sum of the largest prime found in a list and output its original index.
• Write a Python program to scan a list for primes and then determine which prime has the highest value and calculate its digit sum.

Python Code Editor :

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