The selection two (2) is the 2nd beneficial integer and the main prime variety. It is even, and it is the only real even key (the primes apart from 2 are called the odd primes). The variety two can be equivalent to its factorial considering that . 知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 https://ryszardw112kcu0.wonderkingwiki.com/user