Storage: 40 GB available space.

How large is a hive city?

For a 'typical' hive world, a 10-mile high vertical city with the rough surface area of a small European country is probably not a bad guess.

How many people are in a hive city?

A hive city can have on average upwards of 2 trillion inhabitants (that is 2,000,000,000,000 people or 2x10^12, twelve zeroes). There are roughly 1 million inhabited worlds under the control of the Imperium (that is 1,000,000 worlds or 1x10^6, six zeros)