Multiplication order

Hi, 
First of all, great program!
I am not sure if this is intended, but to me the order in which prefixes (n,u,m,k,M,etc) are evaluated is not intuitive.
For instance on 1.5.7:
```
> 1k/1M

1000000000
# wrong value, I suppose it is doing (1E3/1)E6 instead of 1E3/1E6


# i would expect this as the right answer, but using the parenthesis is annoying
>1k/(1M)

0.001
```