The population of the planet would be nearly exactly 1 trillion people, +/- 0.001%, if it were totally covered by land that was as dense as Hong Kong. This is due to the fact that Hong Kong is one of the world's most densely populated regions.
With almost 7,000 people per square kilometre, Hong Kong actually has the highest population density in the entire globe. This suggests that there would be about 7,000 people per square kilometre on Earth if the world's population were as dense as Hong Kong.