I was interested to learn that the 10.000 largest settlements in the world gets you get down to 48.000 population. I’m still trying to work out if that is a surprising figure or not.
In China, you'd reach position 106 before finding a city of less than one million in population (the US has only nine such cities).
India, checking just now, has 46 cities with > 1 million population, the 100th ranked (Malegaon) is 471k, and at #300 population remains > 100k (Aurangabad).
Keep in mind that "city" is a highly arbitrary definition, and some of the world's largest cities would be the equivalent of metropolitan areas or even states or provinces elsewhere.
The largest city by area actually has a remarkably small population: Sermersooq, Greenland, with a population of 24,148 and land area of 575,300 km^2 (220,000 mi^2), which is not only larger than the US state of Rhode Island (by a factor of nearly 144 times), but all but two US states: only Texas and Alaska are larger, and the latter only modestly so (by 12%).
Urban geography is a complicated topic, and typically you'll find that comparisons are made on the basis of multiple scales and definitions such as metropolitan statistical areas (MSAs) and built-up land area, as well as population, which tend to smooth out arbitrary distinctions of political boundaries and give stronger weight to total demographic or economic influence.