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>