Satoshi sets total number of bitcoins to 21 million at line 680 of "main.cpp" file mathematically. above this line there is a comment writted by satoshi: "Subsidy is cut in half every 4 years" link:
https://github.com/Maguines/Bitcoin-v0.1/blob/master/bitcoin0.1/src/main.cpp. if the question be about total number of bitcoins this comment is the answer. if we convert "4" to "four" the result has 32 character and 8 words!
you mistunderstood the whole thing here! most probably because you Ctrl+F searched the number "21" and found that line. which is not even 21 million but 210 thousand.
that line which you posted is not the 21 million limit although it is somewhat related. what is happening there is that every 210000 (210k) blocks we cut the block reward by half. an event known as Halvening these days! and 4 years is the result of time between blocks thanks to difficulty (210000 ~= 4 * 365 * 24 * 6 block/h)
AFAIK nowhere in the source code there is any constant set for maximum number of bitcoins. it just happens to be that much because of the way all these other things are calculated (block reward, block reward halving,...)