In translations they're typically written as numbers, but in the Hebrew text they are (and were) written out as words. For instance, Numbers 1:21:
פְּקֻדֵיהֶם לְמַטֵּה רְאוּבֵן שִׁשָּׁה וְאַרְבָּעִים אֶלֶף וַחֲמֵשׁ מֵאוֹת
The count for the tribe of Reuven: (six and forty) thousand and five hundred.
You can see that the order of words is awkward in English, and probably other languages too, which is why I had to put parentheses for the order of operations. Onkelos, who translated the Torah into Aramaic about 2000 years ago, still wrote the numbers as words but changed the order so that the more significant digits come first:
מִנְיָנֵיהוֹן לְשִׁבְטָא דִּרְאוּבֵן אַרְבְּעִין וְשִׁתָּא אַלְפִין וַחֲמֵישׁ מְאָה.
The count for the tribe of Reuven: (forty and six) thousand and five hundred
Normally if you want to write in English, you would just use numerals
The count for the tribe of Reuven: 46500
unless you want to be flowery, in which case you can write in English words. For example the JPS translation writes:
those that were numbered of them, of the tribe of Reuben, were forty and six thousand and five hundred.
Note they preserve the "and"s, but switch the order as Onkelos does.
(If you want to be really precise, originally Hebrew was written in a different script, but my understanding is that's not what you're asking about.)