7188 /www/nrich/html/content/id/7188/ 1 2011-02-01T00:00:01 <?xml version="1.0" encoding="UTF-8"?> <mdoxml version="1.0"><br></br> <p>Find the number:<br></br>  </p> <div style="margin-left: 40px;">it&#39;s less than $100$;</div> <div style="margin-left: 40px;">it&#39;s one more than a multiple of $3$;</div> <div style="margin-left: 40px;">exactly one of its digits, you get a prime;</div> <div style="margin-left: 40px;">if you reverse its digits, you get a prime;</div> <div style="margin-left: 40px;">it has exactly four factors;</div> <div style="margin-left: 40px;">the sum of its digits is prime;</div> <div style="margin-left: 40px;">if you multiply it by $5$, the answer is greater than $100$.</div> <div> </div> <div> </div> <div>If you liked this problem, <a href="http://nrich.maths.org/5468&amp;part=">here is an NRICH task</a> which challenges you to use similar mathematical ideas. </div> <p> </p> <p> </p></mdoxml> <?xml version="1.0" encoding="UTF-8"?> <mdoxml version="1.0"><br></br> The number is $34$.<br></br>  <br></br>  <br></br></mdoxml> 2 3 0 1 1 0 0 Weekly Problem 35 Numbers and the Number System Factors and multiples Numbers and the Number System Divisibility Numbers and the Number System Prime numbers