A) is 1, just like Alan said.
if all the 20 divisors are the first 20 powers of 2 there will be one prime divisor (That is 2). This number would be 2^19
Any prime to the power of 19 would work just as well I think.
I do not have a pen and paper or a computer. I just have my phone. So I am going to put down my rambling thoughts.
B) Let me think.....
1×2 2factors
1 x2x3. 3+2c2=4factors
1x2x3x5. 4+3c2+3C1=4+3+1=8factors
1×2×3×5×7=
5+4C2+4C3+4C4
=5+6+4+1=16factors
mmm I can't use any more primes....there would be too many factors.
So maybe 4 primes is the most? .....
1×2×3×5×7×2
How many factors does this have?
All the 16 from before plus 12,20,28,60,84,140,420
That makes 16+7=23 factors
thats to many. :(
maybe 3 primes is the mosts.
At this point in time I really need a pen and paper and/or computer and some combinatory mathematics.
But do you get where I am going here?
Like I said. I am really just thinking out loud. There can not be many primes. :(