Re: count zeros in a number

*To*: mathgroup at smc.vnet.net*Subject*: [mg121826] Re: count zeros in a number*From*: Stefan Salanski <wutchamacallit27 at gmail.com>*Date*: Tue, 4 Oct 2011 01:31:26 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j69104$rda$1@smc.vnet.net>

On Oct 2, 2:40 am, dimitris <dimmec... at yahoo.com> 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 All these solutions are very interesting, and they all work, but I believe the simplest solution is actually a built in function, specifically: IntegerExponent[]. IntegerExponent[n,b] returns the highest power of b which divides n, which for b=10, is the number of trailing zeroes of n. moreover, the default value of b is already 10, so that IntegerExponent[n] gives the number of trailing zeroes of n. In[1]:= IntegerExponent[24^24*55^55] Out[1]= 55 http://reference.wolfram.com/mathematica/ref/IntegerExponent.html -Stefan Salanski