I am not a native speaker and I must write a scientific document in American English. How would you correctly write "10000" using LaTeX ?
- with a space only (10 000):
$10\,000$ - with a coma and no space in either side (10,000):
$10{,}000$ - with a coma and a space on its right (10, 000) :
$10,000$
I have seen the second a few times, but I do not know if there is a consensus. Thanks for your help!

siunitxpackage and then\num{10000}. That way you can always change it later. Withoutsiunitx, I would use the first option your suggest:$10\,000$– Peter Grill Nov 21 '18 at 02:08numprintpackage with optionautolanguage(assuming you use babel withamericanorUSenglishclass option) – Nov 21 '18 at 08:33