Depends on where you live, there's no standard.
On the other hand, if writing in English, it makes sense to use the conventions for English, not the German ones just because you might happen to be German.
Numbers consisting of long sequences of digits can be made more readable by separating them into groups, preferably groups of three, separated by a small space. For this reason, ISO 31-0 specifies that such groups of digits should never be separated by a comma or point, as these are reserved for use as the decimal sign.