The square root of 27 to 7 decimal places is 5.1961524
I don't know why my brain thought I needed to carry that information around with me for 25+ years, but there it is.

I also can still quote most of the lyrics to both parts of the ZX Spectrum game "Deus Ex Machina". Egg warm and spinning. Spinning, spinning.
( Michael Ellis contributes nothing, Fri 1 Jul 2011, 13:37, 7 replies)

Or as I remember it
"3-root-2"

Since the square root of two has that "pairs of digits are increasing multiples of 7" thing going on*, it's a very easy one to remember and you then get root-27, root-50, root-98, root-200 and many, many more almost for free.

1.4
14
21
35
63 (OK, it's closer to 62; but good enough for most purposes and easy to remember)
(snopesthetruth, Fri 1 Jul 2011, 13:45, closed)

I have no fucking clue what all that was on about but it sounded great :D

( Michael Ellis contributes nothing, Fri 1 Jul 2011, 13:54, closed)

I was sat in a restaurant with my then girlfriend who happened to be a chartered accountant

we were talking about how quickly the brain can compute maths questions, I said I'm pretty good at that sort of thing, trying to be clever (and show me up a bit) she says 'ok then clever clogs, what's the square root of 361' less than a second later I replied '19'.

God knows how I figured it out that fast but it properly pissed on her chips.
(Kip, Fri 1 Jul 2011, 13:46, closed)

Fish and chips and cycle clips... Hahahahahaha-ha Hahahaha-ha

(An eejit passing by in a purple satin skirt with sparkly bits, Fri 1 Jul 2011, 15:41, closed)

THERE'S ANOTHER ONE! :D

( Michael Ellis contributes nothing, Fri 1 Jul 2011, 15:48, closed)

I can remember little bits of it
Only played the game a couple of times; the soundtrack really was the best bit of it. I've still got the game and its original packaging (acquired at a ZX microfair at Alexandra Palace in the mid-eighties) packed away in a box somewhere.
(An eejit passing by in a purple satin skirt with sparkly bits, Fri 1 Jul 2011, 16:23, closed)

I have only the original packaging - lost the tape and booklet many years ago..
Still, I have the soundtrack on mp3
( Michael Ellis contributes nothing, Fri 1 Jul 2011, 16:36, closed)