[EECS]  820(W, KW or MW) is one of standard numerical values for resistors (of tolerance class 5%). 820pF (picofarads) is one of standard numerical values for capacitors.


[Math.] A triangular number (sum of all integers from 1 to 40): 820 = 1+2+…+39+40 = 1+91+92+93.



[Library]  ISBN-0-821 is the International Standard Book Number for books published by American Mathematical Society.


[Math.]  A prime number.



[Phone]  An area code for the toll-free (or WATS: Wide Area Telecommunications Service.) telephone number, dialing within the U.S. and Canada. Besides the original number 800, there are: 888, 877, 866 and 855 and will be 844, 833 and 822.



[Literature]  A famously long sentence in French literature is of 823-word, in the famous Victor Hugo’s "Les Misérables".


[Math.]  A prime number.



[World]  The ISO country code for United Kingdom of Great Britain & N. Ireland. (ISO-3166)



[Math.]  A prime number.



[Wortd]  The world’s tallest skyscraper, Burj Khalifa, in Dubai, one of the seven emirates of the United Arab Emirates, is 828-meter (2717-foot) high. (January 04, 2010).



[Phone]  The telephone area codes for the Dominican Republic (within U.S./NANPA) are 809 and 829.



[Library]  Numbers 800-899 are the first 3 digits in Dewey Decimal Classification System call numbers for library books in Literature. Numbers 820-829 are for books in English and old English Literature.