Following the third, fourth, or fifth digit, every number up through 15 is the account number while that final number, 16, is the check digit. All Discover cards start with the number six and are 16 digits in length, while petroleum cards start with the number seven and airline cards start with the number one.
Vatican City. Vatican City â 0.2 square miles â The worldâs smallest state, the Vatican has a population of 770, none of whom are permanent residents. The tiny country which surrounds St. Peterâs Basilica is the spiritual center for the worldâs Roman Catholics (over 1 billion strong).
The country with the lowest population density is Greenland (as of 2009) with just 0.067 persons per square mile. (0.027 per square kilometer). Even considered as part of Denmark, the combined population density would still be among the world's five lowest.aiwan, officially known as the Republic of China, has the second  lowest population, but the highest population density in East Asia.  It is smaller than the combined size â¦ of the states of Delaware and  Maryland with an estimated population of 23,373,517, mostly on the  island of Taiwan.