[sidko]

Bitcoin is NOT infinitely divisible. Each Bitcoin is divisible into 10^8. There were reasons to choose this number and isn't arbitrary [1].

[1] https://bitcoin.stackexchange.com/questions/31933/why-is-bit...

[wwwtyro]

It is arbitrarily divisible. Fitting inside 64 bits is convenient, but hardly an insurmountable engineering challenge. There's libraries that handle this sort of thing with ease.