freeCodeCamp/guide/english/certifications/coding-interview-prep/project-euler/problem-3-largest-prime-factor/index.md

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Problem 3: Largest prime factor

Problem 3: Largest prime factor

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Problem Explanation

• To find the largest prime factor of a number, we start from the smallest prime factor 2 and divide the number with it.
• If the remainder is 0 that means the number is divisible by that prime number, we keep dividing the number by same prime number until that number is no more divisible by that prime number.
• After that, we incrememnt the prime factor by 1 and repeat this process till the number becomes 1.

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Solutions

Solution 1 (Click to Show/Hide)

function largestPrimeFactor(number) {
  let prime = 2,
    max = 1;
  while (prime <= number) {
    if (number % prime == 0) {
      max = prime;
      number = number / prime;
    } else prime++; //Only increment the prime number if the number isn't divisible by it
  }
  return max;
}

Relevant Links

• Wikipedia