CHR() and ASCII() have the opposite effect.
The following example gets the characters with the ASCII value of 97, 65, 122, 90, 48, and 57 using CHR().
SQL> SELECT CHR(97), CHR(65), CHR(122), CHR(90), CHR(48), CHR(57) FROM dual;
C C C C C C
- - - - - -
a A z Z 0 9
SQL>