Human Calculators?

Ok, so the other day in maths, we were doing permutations. You know, like "How many different ways can you arrange the letters in the word 'MEDIAN'?" and stuff like that.
With these questions, the Factorial is a commonly used idea, Which looks like this:
8!
And means this:
8x7x6x5x4x3x2x1

Now, Denis, someone in my class, was sitting beside me (Slightly tautological) And he was doing a question that included factorials (Extremely tautological).

And he turns and asks me, I'm guessing somewhat jokingly, what the factorial of 9 was.
Now, at this stage, most people knew the first few factorials. I mean, 4! = 24, 5! = 120, 6! = 720, 7! = 5,040, etc. But most people don't know much further than that.
So when I replied with "362,880", he was a slight bit bewildered at my answering of it.

But then;
See, there's this guy in my school called Conor.

I don't like Conor.

To be honest, he's perturbing at the best of times. At the worst of ti- you know what, I'll leave out the details.

Anyway.
He decided to be all I'mma-catch-you-out-ish and asked me what 11! was.
And I was all like;
"Well, it's 39,916,800."

Like a BAWSS.

Disputatio tibi posterius.