This is very fun, but I don't see a practical use of it

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I remember a friend was giving a speech in front of the class and he just asked "What do you think the number is...". At that moment I just blurted without thought "13". He looked at me as if I was God: "What?! How did you know that?!".
I don't think it is the brain processing information really quickly, because I didn't even know what the question was about.