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>