Cho mình câu trả lời hay nhất nhé: 

uses crt;
var n,m,s,d:longint;
begin
clrscr;
repeat write('Nhap so nguyen duong: ');readln(n);
until n>0;
d:=0; s:=0; m:=n;
repeat
  d:=d+1;
  s:=s+(m mod 10);
  m:=m div 10;
until m=0;
writeln(n,' co ',d,' chu so');
writeln('Tong cac chu so cua ',n,' la ',s);
readln;
end.

program Taylor;
uses crt;
var n,i,tong,a:longint; s:string;
begin
clrscr;
   repeat
      write('Nhap vao 1 so nguyen duong: ');readln(n);
   until n>0;
   str(n,s);
   writeln('So nay co ',length(s),' chu so.');
   for i:=1 to length(S) do
      begin val(s[i],a); inc(tong,a); end;
   writeln('Tong cac chu so cua so do: ',tong);
readln
end.