rev of num

DECLARE
num NUMBER;
rev NUMBER:=0;
rem NUMBER;
copy NUMBER;

BEGIN
num:=#
copy:=num;
WHILE num>0
LOOP
    rev:=rev*10;
    rem:=MOD(num,10);
    rev:=rev+rem;
    num:=TRUNC(num/10);
END LOOP;
DBMS_OUTPUT.put_line('Reverse of '|| copy || ' is ' || rev);
END;