(The meaning of the joke is that the prime number "two" is the oddest, meaning "strangest" as well as a mathematical "odd" number because it is the only even prime number).
（意味は：数字の2は最も奇妙(odd/数学的には奇数を意味する単語)な素数である、何故ならば唯一の偶数の素数(代名詞one）であるから。)