select x,
  to_char((1-to_number(utl_raw.bit_and(substr(x,1,1), '8'))/4)
         *(1+to_number(substr(x, 4), 'xxxxxxxxxxxxx')/power(2,52))
         *power(2,to_number(utl_raw.bit_and(substr(x, 1, 3),'7FF'), 'xxxx')-1023)) y
from (select utl_raw.cast_from_binary_double(447703.37d) x from dual);

X                Y                                       
---------------- ----------------------------------------
411B535D7AE147AE 447703.369999999995343387126922607421875