Japanese prefer odd numbers, whereas Westerners emphasize even numbers, an observation that is clear from the distribution of number-related words in Japanese and English dictionaries. In this article, the author explains why these two cultures differ by surveying the history of numbers, including yin-yang thought from ancient China, ancient Greek philosophy, and modern European mathematics. The author also mentions that oddness and evenness are only mathematical concepts, but understanding the cultures and histories of individual countries contributes to world peace. (Contains 1 figure.)