Get number digits

[Aphton]

Here are the mathematical fucntions you need:

digitCount(x) := ⌈log10(x+1)⌉
extractDigit(x, digitIdx) := ⌊x / 10^(digitCount(x)-digitIdx)⌋ mod 10

(sidenote - "⌈⌉" stands for ceiling, "⌊⌋" for flooring)

Example number = 1234
digitCount(1234) = ⌈log10(1234+1)⌉
= ⌈3.09⌉
= 4

extractDigit(1234, 2) = ⌊1234 / 10^(4 - 2)⌋ mod 10
= ⌊1234 / 10^2⌋ mod 10
= ⌊1234 / 100⌋ mod 10
= ⌊12.34⌋ mod 10
= 12 mod 10
= 2

Edit: This is mathematically as low as it gets.. Cant think of a shorter way right now.
Bitshifting works on base 2. You would have to remap which is an extra overhead that is not needed.
There are assembler instructions (SSE, SSE2, ..) that are faster.
As far as I know the math.pas functions use the optimized assembler operations. Use it!