Which of the following numbers has only one prime factor?  Pick: A) 16 B) 19 C) 22 D) 30 E) 32
16=2^4   19=19   22=2*11   30=2*3*5   32=2^5   19 has 1 distinct prime factor   Answer 19
<result>B</result>
Which of the following numbers has only one prime factor?