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id	challengeType	title	forumTopicId
5900f3b21000cf542c50fec5	5	Problem 70: Totient permutation	302183

Description

Euler's Totient function, φ(n) [sometimes called the phi function], is used to determine the number of positive numbers less than or equal to n which are relatively prime to n. For example, as 1, 2, 4, 5, 7, and 8, are all less than nine and relatively prime to nine, φ(9)=6.The number 1 is considered to be relatively prime to every positive number, so φ(1)=1. Interestingly, φ(87109)=79180, and it can be seen that 87109 is a permutation of 79180. Find the value of n, 1 < n < 107, for which φ(n) is a permutation of n and the ratio n/φ(n) produces a minimum.

Instructions

Tests

tests:
  - text: <code>euler70()</code> should return 8319823.
    testString: assert.strictEqual(euler70(), 8319823);

Challenge Seed

function euler70() {
  // Good luck!
  return true;
}

euler70();

Solution

// solution required

1.2 KiB Raw Blame History