submitted 5 months ago by Hamartiogonic@sopuli.xyz to c/unexpectedfactorial@sopuli.xyz

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18! = 6 402 373 705 728 000

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[-] Hamartiogonic@sopuli.xyz 2 points 5 months ago

Oh that’s a good point. My mind isn’t constantly looking for upside down exclamation marks, so definitely missed that one.

this post was submitted on 19 Mar 2026

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Unexpected Factorial

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When you use an exclamation mark with a number, you’re actually implying it’s not a normal number any more. It’s a factorial!

Ok, so how does this work?

5!=1×2×3×4×5=120

6!=720

These numbers get really large. For example:

15!≈1.3×10^12

So, next time you see a headline with 2000! in it, you’ll know what to expect.

There are also double factorials (n!!) and iterated factorials (n!)!, and they aren’t the same thing. Just add more exclamation marks and you get multifactorial. Check wikipedia to see how spicy it gets.

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