I dont think Oracle has a datatype to hold numbers greater than 1E+125 as even the ansi standard datatypes are just mapped onto number. The funny thing is the Oracle Number datatype holds numbers to a far higher precision than double as it can be upto 21 bytes in size if I recall correctly.
I have had a similar problem to this before. I used two columns, one to store the prefix and the other to store the exponent. When you need to work with the number select both rows and then calculate the full number in your Java / C program.