求助

miafy

20.
                2942-!-item-!-187;#058&003104

For any positive integer n, the length of n is defined as the number of prime factors whose product is n.  For example, the length of 75 is 3, since 75 = 3 ?? 5 ?? 5.  How many two-digit positive integers have length 6 ?

 

(A) None

(B) One

(C) Two

(D) Three

(E) Four

答案是Ｃ可不可以帮忙解释一下

Tracylee03

只有两个数,即日64=2^6  ,96=2^5X3,其他的都不行.