Python Program for Find largest prime factor of a number

Given a positive integer \’n\'( 1 <= n <= 1015). Find the largest prime factor of a number.

Input: 6
Output: 3
Explanation
Prime factor of 6 are- 2, 3
Largest of them is \'3\'

Input: 15
Output: 5

Python3

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# Python3 code to find largest prime
# factor of number
import math
  
# A function to find largest prime factor
def maxPrimeFactors (n):
      
    # Initialize the maximum prime factor
    # variable with the lowest one
    maxPrime = -1
      
    # Print the number of 2s that divide n
    while n % 2 == 0:
        maxPrime = 2
        n >>= 1     # equivalent to n /= 2
          
    # n must be odd at this point, 
    # thus skip the even numbers and 
    # iterate only for odd integers
    for i in range(3, int(math.sqrt(n)) + 1, 2):
        while n % i == 0:
            maxPrime = i
            n = n / i
      
    # This condition is to handle the 
    # case when n is a prime number 
    # greater than 2
    if n > 2:
        maxPrime = n
      
    return int(maxPrime)
  
# Driver code to test above function
n = 15
print(maxPrimeFactors(n))
  
n = 25698751364526
print(maxPrimeFactors(n))
  
# This code is contributed by "Sharad_Bhardwaj".

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Output:

5
328513

Time complexity: \text{O}(\sqrt{n})
Auxiliary space: \text{O}(1)

Please refer complete article on Find largest prime factor of a number for more details!



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