1 000 000 - the most round number in practice ?

[JaanusRaim]

In theory, the round numbers are all that can be divided by 10.  In practice, we all have experienced that 10 000 is more useful than 100 000 and 100 000 000 is more useful than 10 000 000.
To win the competition of "practical roundness" its number of zeros can not be a prime number at all, it has to be divided as many ways as possible and be as small as possible at the same time.
1 000 000 that is both square of 1000 and cube of 100 seems to have only one possible competitor in that usefulness - 1 000 000 000 000 but it is already too far from everyday working places.