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Re: count zeros in a number

  • To: mathgroup at smc.vnet.net
  • Subject: [mg121811] Re: count zeros in a number
  • From: Peter Pein <petsie at dordos.net>
  • Date: Mon, 3 Oct 2011 04:23:10 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <j69104$rda$1@smc.vnet.net>

Am 02.10.2011 08:40, schrieb dimitris:
> 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
>

Using pattern matching makes this an easy one :-)

In[1]:= TrailingZeros[n_Integer] :=
   IntegerDigits[n] /. {___, Except[0], z: ((0) ...)} :> Length[{z}]

TrailingZeros[24^24 55^55]
Out[2]= 55




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