最大的质数到底有多大？

A prime number is very special. 质数是种很特别的数。 It can only be divided by 1 and itself. 它只能被1和它自己整除。 2, 3, 5, 7 and 11 are small primes. 2、3、5、7、11，都是小质数。 Big primes are much harder to find. 大质数呀，难找得不得了。 People use huge computers to look for them. 人们用超大电脑，一个劲儿找它。 The biggest known prime has millions of digits. 目前最大的质数，有几百万位。 But there is always a bigger one waiting. 而更大的那个，永远还在前头等着。 Primes never, ever come to an end. 质数呀，根本数不到头。