Belgium is 2.2 times larger than Montenegro.
Area: 30,528 km2 World Factbook
Population: 10,449,361 (July 2014) World Factbook
Belgium, officially the Kingdom of Belgium, is a federal monarchy in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters as well as those of several other major international organisations such as NATO. Wikipedia
Area: 13,812 km2 World Factbook
Population: 650,036 (July 2014) World Factbook
Montenegro is a country in Southeastern Europe. It has a coast on the Adriatic Sea to the south-west and is bordered by Croatia to the west, Bosnia and Herzegovina to the northwest, Serbia to the northeast, Kosovo to the east and Albania to the south-east. Wikipedia