Let's call it "Bitliquid". Since liquid is uncountable, we'll measure it in liters, and talk about sending 21.5 liters of bitliquid. Divisibility problem solved. 
i like this metaphor, though liquid is perfectly countable, on the level of sub-atomic particles (this is tricky in the real world, but since we're using fictional particles, it works), which we can define as 0.00000001 BTC. and if we consider 1 BTC as a litre, we can work from that using standard prefixes. 0.001 is a millilitre and so on.
we could always call it latinum. =)