It is 1) 2n-1 where n is the no. of prime factors of N.
Let N= p1a1 p2a2....pnan Each prime factor can either go to the first factor or the second factor. since the two factors are relatively prime ,we cannot choose the power of pi in a factor. If a factor say p1 is going to the first factor, then p1 should completely go to the first factor and so on. So the no. of ways is 2n
Finally , each factorization appears 2 times ( ab and ba) so we divide the answer by 2.