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<!DOCTYPE html>
<html lang=en>
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  <meta charset=utf-8>
  <title>Power of 3 check</title>
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<body>
  <h1>Power of 3 check</h1>
  <pre id=out></pre>
  <script>!function(){var n=[];n.push("Input: 27"),n.push(function(n){if(n<=0)return!1;for(;n%3==0;)n/=3;return 1===n}(27)?"27 is a power of 3.":"27 is not a power of 3."),document.getElementById("out").textContent=n.join("\n")}()</script>
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JavaScript Power of 3 — Single Number (Try It)