Just general advice for anyone that noticed this is awkward to read, when you have to write two numbers back to back like this, do one as letters.
One 10000 person protest or ten 1000 person protests. Alternately, all as letters also works. But numbers in a sentence tend to pop more.
Standard practice is to do the simpler number as words and the more complicated number as numbers.
1 ten thousand person protest or 10 one thousand person protests doesn't look as good, despite still being better than all numbers.