I have a table with two columns. In the first column `X` there are numbers from 1 to 10000. The second column `Y` is empty. This is how I set this up:

```
create table test1 (
  x number,
  y number
);

begin
  for l in 1..10000 LOOP
    insert into test1(x)
    values(l);
  end loop;
  commit;
end;

```

My first question is: I need to use an update statement to set the values of column `Y` in the reverse order to those in column `X`, i.e. from 10000 to 1. The row with X=1 needs to have Y=10000; the row with X=2 needs to name Y=9999; etc. How can I do that?

My second question is: how can I do a math operation (SQL or PL/SQL) 
which will leave in the column only those numbers which can be divided to 17?