For how many positive integers is the number of positive divisors equal to the number itself ?  Options
A) none
B) one
C) two
D) three
E) cannot be determined
The factors of 1: {1}. 1 factor. WORKS!   The factors of 2: {1,2}, 2 factors. WORKS!   The factors of 3: {1,3}, 2 factors. Doesn't work   The factors of 4: {1,2,4}, 3 factors. Doesn't work   As we can see, if an integer n has n factors, then the factors of n must be: {1, 2, 3,....., n)   So, we can quickly see that the only positive integers that meet this criterion are 1 and 2   Answer:one
<result>B</result>
For how many positive integers is the number of positive divisors equal to the number itself ?