You can do that, sort of. You might not want to because you might be suggesting non-existent accuracy.
format(123456789101112131415161718192021,"Fixed Dec", Use thousands separator( 1 ), 60, 0)
// "123,456,789,101,112,139,099,124,663,320,576"
Notice there are only 15 to 16 significant digits; the remainder are garbage. This is a function of the IEEE 8-byte double precision floating point representation that can only represent an integer up to about 2^53==9007199254740992 (all 15 digit integers and most 16 digit integers.)
The 60, above, probably will break down around 100 as well. It does include the commas.
Craige