<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta charset="utf-8">
<title>Problem 20 - Project Euler</title>
<link rel="shortcut icon" href="favicon.ico">
<link rel="stylesheet" type="text/css" href="pe_template_style.css">
<script type="text/x-mathjax-config">
MathJax.Hub.Config({
jax: ["input/TeX", "output/HTML-CSS"],
tex2jax: {
inlineMath: [ ["$","$"], ["\\(","\\)"] ],
displayMath: [ ["$$","$$"], ["\\[","\\]"] ],
processEscapes: true
},
"HTML-CSS": { availableFonts: ["TeX"] }
});
</script>
<script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_HTML">
</script>
<script type="text/javascript" src="md5.min.js"></script>
<script type="text/javascript">
function check_ans(ans) {
if (md5(ans) === "443cb001c138b2561a0d90720d6c111") {
alert("Correct!");
} else {
alert("Sorry, that is incorrect!");
};
};
</script>
</head>
<body>
<div id="container">
<div id="nav" class="noprint">
<ul>
<li><a href="about.html" title="About">About</a></li>
<li id="current"><a href="problems.html" title="Problems">Problems</a></li>
<li><a href="news.html" title="News">News</a></li>
<li><a href="http://forum.projecteuler.net" title="Project Euler Forum">Forum</a></li>
</ul>
<div style="text-align:right;padding:30px 10px 0 0;">
<a href="rss2_euler.xml"><img src="images/icon_rss.png" alt="RSS Feed" title="RSS Feed"></a>
</div>
</div>
<div id="logo" class="noprint">
<img src="images/pe_banner.png" alt="Project Euler .net">
</div>
<div id="content">
<div id="notification">This website is a semi-functional mirror of the original <a href="https://projecteuler.net/">Project Euler</a>. More information is available on <a href="https://github.com/wackyapples/ProjectEulerMirror/blob/gh-pages/README.md">GitHub</a>.</div>
<div style="text-align:center;" class="print"><img src="images/pe_banner.png" alt="projecteuler.net" style="border:none;"></div>
<h2>Factorial digit sum</h2>
<h3>Problem 20</h3>
<div style="font-size:80%;color:#999;">Published on 21 June 2002 at 06:00 pm [Server Time]</div>
<div class="problem_content" role="problem">
<p><i>n</i>! means <i>n</i> × (<i>n</i> − 1) × ... × 3 × 2 × 1</p>
<p>For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,<br>and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.</p>
<p>Find the sum of the digits in the number 100!</p>
</div>
<br>
<div style="text-align:center;" class="noprint">
Answer: <input type="text" name="answer" id="answer" style="border:1px solid #999;width:100px;">
<button onclick="check_ans(document.getElementById('answer').value);">Check</button>
</div>
<script type="text/javascript">document.getElementById('answer').focus();</script><div>Go to back to <a href="problems%3Bpage=1.html">Problems</a>
</div>
</div>
<div id="footer" class="noprint">© Project Euler</div>
<!--/Creative Commons License--><!-- <rdf:RDF xmlns="http://web.resource.org/cc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
<Work rdf:about="">
<license rdf:resource="http://creativecommons.org/licenses/by-nc-sa/2.0/uk/" />
<dc:type rdf:resource="http://purl.org/dc/dcmitype/Text" />
</Work>
<License rdf:about="http://creativecommons.org/licenses/by-nc-sa/2.0/uk/"><permits rdf:resource="http://web.resource.org/cc/Reproduction"/><permits rdf:resource="http://web.resource.org/cc/Distribution"/><requires rdf:resource="http://web.resource.org/cc/Notice"/><requires rdf:resource="http://web.resource.org/cc/Attribution"/><prohibits rdf:resource="http://web.resource.org/cc/CommercialUse"/><permits rdf:resource="http://web.resource.org/cc/DerivativeWorks"/><requires rdf:resource="http://web.resource.org/cc/ShareAlike"/></License></rdf:RDF> -->
</div>
<div style="height:1px;"> </div>
</body>
</html>