What's the correct syntax for setting a value to a number item using a literal

Just to be sure: is there any difference (or the other way round: whats the correct syntax to use) when setting a literal to a NumebrItem, in this case a temperature value to a thermostat.

[ ] wbf1_roomR_therm0_tempSet.sendCommand(“21”)
[ ] wbf1_roomR_therm0_tempSet.sendCommand(21)
[ ] wbf1_roomR_therm0_tempSet.sendCommand(21.0)


I think that all three are valid for setting an item. Where people run into trouble is when trying to get the value of a Number item as a literal.