n=91

by v_Enhance, Apr 28, 2011, 10:00 PM

Conway says that this is the first number to look prime but be composite.

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7 Comments

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Hmm

51 maybe?

by AwesomeToad, Apr 28, 2011, 10:08 PM

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Nah, sum digits makes it obvious.

by v_Enhance, Apr 28, 2011, 10:09 PM

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I'd defintely think 51, or maybe 57. 91 does look prime, though.

by apple.singer, Apr 28, 2011, 11:07 PM

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I'm already used to 91 being composite so it doesn't look prime to me anymore. :P

by 3333, Apr 28, 2011, 11:33 PM

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You guys are missing the point.

by v_Enhance, Apr 28, 2011, 11:34 PM

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I get it now.

by AwesomeToad, Apr 29, 2011, 1:23 AM

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Difference of squares trivializes this


119 looks like a prime.
This post has been edited 1 time. Last edited by james4l, Apr 29, 2011, 2:22 AM

by james4l, Apr 29, 2011, 2:15 AM

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