Basic misses a publicly available 64-bit integer type. This is problematic in several aspects.

1. It limits the calculation range.
2. It breaks compatibility with VBA [1].
3. It disallows using external API that uses 64-bit integral types or pointers (like window handling WinAPI that operates with HANDLE, which is platform-dependent type which size is equal to respective platform pointer size).
4. It makes it problematic to use UNO API that works with 'hyper' UNO type [2].

But the code to handle 64-bit data is already there (at least to some extent): e.g., see [3].

We need to add respective keyword, type character, conversion functions, etc. to make it first-class type among other available types.

[1] https://docs.microsoft.com/en-us/office/vba/Language/Reference/User-Interface-Help/longlong-data-type
[2] https://opengrok.libreoffice.org/search?full=hyper&path=idl&project=core
[3] https://opengrok.libreoffice.org/xref/core/basic/source/sbx/sbxint.cxx?r=840b4eb2#314