document.write( "Question 692741: the number of numbers less than 21 and relatively prime to 21 is \n" ); document.write( "

Algebra.Com's Answer #455093 by tommyt3rd(5050) $\"\"$ $\"About$

You can put this solution on YOUR website!
There is a famous function to compute this number, the euler totient function, when you get a chance you can look it up :)\r
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\n" ); document.write( "\n" ); document.write( "For now we'll compute directly since 21 is relatively small\r
\n" ); document.write( "\n" ); document.write( "1, always
\n" ); document.write( "21/2=10 r 1 yes
\n" ); document.write( "21/3=7 r 0 no
\n" ); document.write( "21/4 => r 1 yes
\n" ); document.write( "21/5 yes
\n" ); document.write( "21/6 r 3 no
\n" ); document.write( "21/7 no
\n" ); document.write( "21/8 yes
\n" ); document.write( "21/9 no
\n" ); document.write( "21/10 yes
\n" ); document.write( "21/11 yes
\n" ); document.write( "21/12 no
\n" ); document.write( "21/13 yes
\n" ); document.write( "21/14 no
\n" ); document.write( "21/15 no
\n" ); document.write( "21/16 yes
\n" ); document.write( "21/17 yes
\n" ); document.write( "21/18 no
\n" ); document.write( "21/19 yes
\n" ); document.write( "21/20 yes
\n" ); document.write( "21/21 no\r
\n" ); document.write( "\n" ); document.write( "so the count is...12\r
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\n" ); document.write( "\n" ); document.write( ":) \n" ); document.write( "

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