Nauru is about 658 times smaller than Montenegro.

Montenegro is approximately 13,812 sq km, while Nauru is approximately 21 sq km, making Nauru 0.15% the size of Montenegro. Meanwhile, the population of Montenegro is ~604,966 people (595,155 fewer people live in Nauru).
Tip: This to-scale comparison of Montenegro vs. Nauru uses the Mercator projection, which distorts the size of regions near the poles.
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