Japanese counting is a bit different than English counting. We have words for hundred, thousand, million, billion, etc. In that order. To express points in between, we’ll say things like “ten thousand”, “four million”, etc.
Japanese also has words for ten (ju), hundred (hyaku) and thousand (sen), but they also have a unique word for ten-thousand (man). So to express the idea of “100,000” they wouldn’t say “hundred thousand” then would say “ju man” (ten ten-thousands). They don’t have a word for million, they would instead say “hyaku man” (hundred ten-thousands). Ten-million is “sen man” (thousand ten-thousand).
Here’s where it gets interesting- they wouldn’t say “man man” (ten thousand ten thousand) so they have a unique word for hundred-million, “oku”. They also wouldn’t say “man oku” (ten-thousand hundred-million, known to us as “trillion”) so they would instead say “chou”.
All this said, they can technically express the idea of “millionaire” (hyakumanchouja) but they’d probably sooner go to this term “okumanchouja”, where “oku” is chouja refers to the person, “oku” is hundred-million, and while “man” technically means ten-thousand, in this case, it’s more of an emphatic to imply a great number of things.