Representing big numbers in source code for readability?

Question

Is there a more human-readable way for representing big numbers in the source code of an application written in C++ or C?

let\'s for example take the number 2,

Answer 1

With Boost.PP:

#define NUM(...) \
    NUM_SEQ(BOOST_PP_VARIADIC_TO_SEQ(__VA_ARGS__)) 
#define NUM_SEQ(seq) \
    BOOST_PP_SEQ_FOLD_LEFT(NUM_FOLD, BOOST_PP_SEQ_HEAD(seq), BOOST_PP_SEQ_TAIL(seq)) 
#define NUM_FOLD(_, acc, x) \
    BOOST_PP_CAT(acc, x)

Usage:

NUM(123, 456, 789) // Expands to 123456789

Demo.

Another way is making an UDL. Left as an exercise (and also because it requires more code).