Two numbers are said to be ‘relatively prime’ if their greatest common factor is 1

2 and 9 are relatively prime. Because they share no common factors:

  • 2: factors [1, 2]
  • 9: factors [1, 3, 9] No number other than “1” is shared. Therefore they are, by definition, relatively prime.

9 and 27 are not relatively prime, because their Greatest Common Factor is > 1 (it’s 3).


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