[NumLock]

Код:

var
  s: String;
  i: Integer;
begin
  s:='123qwe';
  for i:=1 to Length(s) do if not (s[i] in ['0'..'9']) then Break;
  s:=PChar(@s[i]);
  ShowMessage('"'+s+'"'+#13#10+IntToStr(Length(s)));
end;