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threelonmusketeers@sh.itjust.works to Math Memes@lemmy.blahaj.zoneEnglish · 9 months ago

John Conway proves that 91 is the smallest number which looks prime but isn't

www.youtube.com

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John Conway proves that 91 is the smallest number which looks prime but isn't

www.youtube.com

threelonmusketeers@sh.itjust.works to Math Memes@lemmy.blahaj.zoneEnglish · 9 months ago
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  • mvirts@lemmy.world
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    9 months ago

    No it’s 51

    • TunaCowboy@lemmy.world
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      9 months ago

      Naw, 5 + 1 = 6, 6 is divisible by 3, so 51 is divisible by 3.

      • OpenStars@discuss.online
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        9 months ago

        img

      • xpinchx@lemmy.world
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        9 months ago

        I shared this at work recently and nobody cared. 3 6 and 9 are all kinda special.

    • I'll be on ShareMySims@lemmy.dbzer0.com@sh.itjust.works
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      9 months ago

      Only if you weren’t taught (or were, but too long ago lol) the divisible by 3 rule - if the sum of the digits is divisible by 3, so is the whole number. 5+1=6 therefore 51 is divisible by 3! Bonus division rule - if it was also an even number and therefore divisible by 2, you could deduce that the whole number was divisible by 6.

      • Xtallll@lemmy.blahaj.zone
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        9 months ago

        Actually 51/3! Is 8.5

        • Cadeillac@lemmy.world
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          9 months ago

          You bastard

        • threelonmusketeers@sh.itjust.worksOP
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          9 months ago

          !unexpectedfactorial@sopuli.xyz

      • Nougat@fedia.io
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        9 months ago

        Actually, 51 is not divisible by 3!

        It is divisible by 3

        • I'll be on ShareMySims@lemmy.dbzer0.com@sh.itjust.works
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          8 months ago

          Hilarious.

    • smeg@feddit.uk
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      8 months ago

      Surely it’s 1? Looks prime, and some people will even argue that it is!

      • mvirts@lemmy.world
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        8 months ago

        Its only factors are 1 and itself after all

    • demonmittenhands@lemmy.world
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      9 months ago

      Agreed. 51 looks prime AF.

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