Guam Business Directory: GUM is the ISO 3 alphabet country code of Guam. Currency of Guam is $, which has a short code of USD. Capital of Guam is Hagatna. Guam has the population of 165718 and approximate area is 544.00 square kilometers (or approx. 338.0416 square miles). Population density of Guam is approx. 304/Km2 (or approx. 188.9056/mile2)