You might see some examples using the JSP format to spell a number, eg

SQL> select to_char(to_date('7','J'),'JSP') from dual;

TO_CH
-----
SEVEN

but that wont work here, because zero is not allowed

SQL> select to_char(to_date('0','J'),'JSP') from dual;
select to_char(to_date('0','J'),'JSP') from dual
                       *
ERROR at line 1:
ORA-01854: julian date must be between 1 and 5373484

So we'll just use a simple CASE statement, and "connect by level" to cycle through each character

SQL> select
  2    case x
  3      when '0' then 'zero'
  4      when '1' then 'one'
  5      when '2' then 'two'
  6      when '3' then 'three'
  7      when '4' then 'four'
  8      when '5' then 'five'
  9      when '6' then 'six'
 10      when '7' then 'seven'
 11      when '8' then 'eight'
 12      when '9' then 'nine'
 13    end
 14  from ( select '3' x from dual ) ;

CASEX
-----
three

SQL>
SQL>      select
  2    case x
  3      when '0' then 'zero'
  4      when '1' then 'one'
  5      when '2' then 'two'
  6      when '3' then 'three'
  7      when '4' then 'four'
  8      when '5' then 'five'
  9      when '6' then 'six'
 10      when '7' then 'seven'
 11      when '8' then 'eight'
 12      when '9' then 'nine'
 13    end
 14  from (
 15    select substr('123',rownum,1) x
 16    from dual
 17    connect by level <= 3
 18    ) ;

CASEX
-----
one
two
three

So now we just need to incorporate that into our table of values. Here's how we can get each element within each row of a table

SQL> create or replace type string_list is table of varchar2(20);
  2  /

Type created.

SQL>
SQL> create table t ( x int );

Table created.

SQL>
SQL> insert into t values (101);

1 row created.

SQL> insert into t values (456);

1 row created.

SQL> insert into t values (789);

1 row created.

SQL>
SQL> select *
  2  from t,
  3       table(cast(multiset(
  4          select substr(to_char(t.x),rownum,1)
  5          from dual
  6  connect by level <= length(to_char(t.x))) as string_list)
  7  );

         X COLUMN_VAL
---------- ----------
       101 1
       101 0
       101 1
       456 4
       456 5
       456 6
       789 7
       789 8
       789 9

9 rows selected.

so now we just incorporate our case statement and we're nearly there

SQL> select
  2    x,
  3    case digit
  4      when '0' then 'zero'
  5      when '1' then 'one'
  6      when '2' then 'two'
  7      when '3' then 'three'
  8      when '4' then 'four'
  9      when '5' then 'five'
 10      when '6' then 'six'
 11      when '7' then 'seven'
 12      when '8' then 'eight'
 13      when '9' then 'nine'
 14    end str
 15  from (
 16    select x, column_value digit
 17    from t,
 18         table(cast(multiset(
 19            select substr(to_char(t.x),rownum,1)
 20            from dual
 21    connect by level <= length(to_char(t.x))) as string_list)
 22    )
 23  )
 24
SQL>
SQL>
SQL> /

         X STR
---------- -----
       101 one
       101 zero
       101 one
       456 four
       456 five
       456 six
       789 seven
       789 eight
       789 nine

9 rows selected.

Now we need to aggregate those strings - on 11g upwards you can use LISTAGG but since you're on 10g you'll need to roll your own. See the examples in this question for details.

https://asktom.oracle.com/pls/apex/asktom.search?tag=stragg#16551777586484

Then it will just be

select x, stragg(str)
from
( ... the above )
group by x