The documentation I recently posted for Script BASIC flushed out a command I was unaware of.
MININT
This built-in constant is implemented as an argument less function. Returns the minimal ("maximal negative") number that can be stored as an integer value.
Output from my Ubuntu 14.04 LTS 64 bit laptop.
jrs@laptop:~/sb/sb22/test$ scriba minint.sb
-9223372036854775808
jrs@laptop:~/sb/sb22/test$