Re: count zeros in a number
- To: mathgroup at smc.vnet.net
- Subject: [mg121802] Re: count zeros in a number
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Mon, 3 Oct 2011 04:21:32 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <201110020636.CAA28027@smc.vnet.net>
On 2 Oct 2011, at 08:36, dimitris wrote:
> Hello.
>
> Consider e.g. the number 24^24*55^55.
> This number ends with exactly 55 zeros as the following demonstrate
>
> In[201]:= Mod[24^24*55^55, 10^55]
> Mod[24^24*55^55, 10^56]
>
> Out[201]= 0
> Out[202]= 20000000000000000000000000000000000000000000000000000000
>
>
> What I want now is a way to count the zeros that a number ends without
> knowing in advance this number of zeros like in the above example.
>
> Thanks in advance.
> Dimitris
>
Probably the most obvious way is to let Mathematica multiply out the numbers and count the trailing zeros, eg.
Length[Last[Split[IntegerDigits[24^24*55^55]]]]
55
An alternative approach is to just count the exponents of 5 and 2 and take the smaller one:
Min[
Cases[FactorInteger[24^24*55^55], {2, x_} | {5, y_} :> {x, y}]]
55
Andrzej Kozlowski
- References:
- count zeros in a number
- From: dimitris <dimmechan@yahoo.com>
- count zeros in a number