Fuzzing numerals to numerals

Some fuzzers can be categorized as "input fuzzers". Given a program input, they mutate it and generate another input, which has the potential to crash the program.

Now, I need to fuzz numerals and I hope the output of the fuzzers are numerals as well. E.g. an int64 integer should become another int64. An binary64 float should transform to another binary64, etc.

Question: which fuzzer(s) can fuzzing numerals to numerals?

I tried radamsa and zzuf. They keep giving me invalid numerals. For example, with radamsa,

echo "23" | radamsa -n 5

gives me something like

1
2333
--2571768211456
               15270973215354030929899885800935293
-1#

Of course, one could simply discard invalid inputs, but I suppose that is not efficient. So I wonder whether there exists some kind of grammar-based fuzzers that can fuzz numerals to numerals? Thanks.