TITLE: How would you count a base $> 36$ system?
QUESTION [13 upvotes]: When I am counting in a base greater than ten, I can use the letters of the alphabet.  What do I use when I run out of those?
What comes after $z$?:
$0, 1, 2, 3,\ldots, 9, a, b, c, d,\ldots, x, y, z$ (?)
And how would I find it?

REPLY [3 votes]: I don't mean to be silly, but why not use base 6?  If you want join the gitis in groups of two bits
1234123051 can be understood as a 5-digit number:
12 34 12 30 51
In the decimal system multiplying by ten $T: x\mapsto 10x$ plays a very special role.  
If we want to learn about a number $\alpha$  we could take the integer part (e.g. $\lfloor 3.5\rfloor = 3$), then multiply by 10, take the integer part again.  Doing this over and over would give our decimal system.

$10^0\pi \mapsto 3$
$10^1\pi \mapsto 1$
$10^2\pi \mapsto 4$
...

In your case, using 36 instead of 10.  Or just use two base-6 digits.  This is also related to channel coding from information theory.