Number 15

A page of the Numeropedia - the Special Encyclopedia of Numbers

[10-19]:  10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19

All Numbers  &   [0-9]  &  10-19    20-29  30-39  40-49  50-59  60-69  70-79  80-89  90-99  100

1  - 10 - 100  - 1000 - 10,000 - 100,000 - 1M - 10M - 100M1B10B - 100B - 1T - 10T - 100T - 1Q - ...

Number 15 in Math.     Number 15 in Sports    Number 15


[Calendar]  The “Ides of March” is March 15, the fateful day Julius Caesar was assassinated in the year 44 B.C.


[Chemistry]  The atomic number of Phosphorous (P).


[Chemistry]  The number of chemical elements in the Lanthanide series: Lanthanum (57) to Lutetium (71) and in the Actinide series: Actinium (89) to Lawrencium (103).


[EECS]  In hexadecimal number system, F = 15.


[EECS]  15(W, KW or MW) is one of standard numerical values for resistors (of tolerance class 5%). 15pf (picofarads) and 15mF (microfarads) are two of standard numerical values for capacitors.


[Flag]  Twelve stars form a circle on the middle of the European Union flag, representing the first 12 nations (when founded on 1 November 1993): Belgium, Denmark, France, Germany, Greece, Ireland, Italy, Luxemburg, Netherlands, Portugal, Spain and United Kingdom. The next 3 members since 1 January 1995 are: Austria, Finland and Sweden. (Ten newest members: Poland, Hungary, Slovakia, Slovenia, Malta, Lithuania, Czech Republic, Estonia, Latvia and Cyprus (2004). Three new candidates: Bulgaria, Romania and Turkey. Two applications pending: Croatia and Macedonia, as of 2005.)

The block of the first 15 countries of European Union is called EU-15.


[Flag]  The number of white stars forming a circle on the national flag of Cook Islands, representing its 15 islands.


[Game]  The “15-puzzle” (invented by Sam Loyd, 1878) is played on a 4×4 square board consisting of 15 square pieces, numbered 1-15 initially arranged in ascending order, with an empty square at the board’s bottom right corner.


[Game]  Each player has 15 counters at the start of the game of backgammon.


[Game]  The size of a Scrabble board is 15×15, i.e. having 225 squares for 100 numbered letter tiles used in the game and 7 letters on each player’s rack at a time.


[Geology]  A time zone theoretically spans equally 15o of longitude, but actual time zones have irregular boundaries.


[Geology]  The angular velocity at which the Earth rotates around its axis: 15o per hour; it is called earth-rate unit (eru), used to measure the drift rates of gyroscopes in aerospace engineering.


[Geology]  I-15, a major U.S. North-South interstate highway, connecting Sweetgrass, Montana (at Canada border) to San Diego, California, 1437 miles. 


[Gov.]  In Iowa caucuses, Democrats are asked twice: an initial question for support of a candidate and a second if their first choice candidate does not reach the 15% threshold of viability.


[Gov.]  Homeland Security Department became the 15th U.S. President’s Cabinet-level departments, on 25 November 2002, whose first Secretary, Tom Ridge, sworn in 24 January 2003.

All the U.S. Departments are: (1) State (2) Treasury, (3) Defense, (4) Justice, (5) Interior, (6) Agriculture, (7) Commerce, (8) Labor, (9) Health and Human Services, (10) Housing and Urban Development, (11) Transportation, (12) Energy, (13) Education, (14) Veterans’ Affairs and (15) Homeland Security. 


[Gov.]  The number of salary grades in the most popular General Schedule (GS) salary pay scale for the U.S. government employees (civil servants). Each grade has 10 steps, 01-20.


[History] Kentucky became the 15th state of the U.S. on 1 June 1792.


[History]  The 15th U.S. President: James Buchanan (Democrat, Pennsylvania, 1857-1861).

His Vice President, John Cabell Breckinridge (Kentucky), was the 14th U.S. Vice President.


[History]  The number of stars on the Fort McHenry flag that inspired the “Star-Spangled Banner”, which was officially made the national anthem by U.S. Congress in 1931. (Written by Francis Scott Key in Sept. 1814).


[History]  U.S. Hispanic Heritage month is from September 15 to October 15.


[Language]  Prefixes: Quinde-, Qunidec-, Pendeca-,...


[Language]  The only 15-letter English word that has no repeating letter is uncopyrightable.


[Library]  ISBN-0-15 is the International Standard Book Number for books published by Harcourt Brace Jovanovich.


[Money]  The number of digits of a credit card or ATM card number is 13 (Visa), 14 (Diners Club/Carte Blanche), 15 (American Express, JCB, enRoute) or 16 (Discover, MasterCard, Visa, JCB).


[Movie]  The duration (seconds) that a rating symbol (in the 1997 rating system of 6 basic ratings: TV-Y, TV-G, TV-Y7, TV-PG, TV-14 and TV-M) appearing in the upper left corner of the screen at the beginning of each show, except news and sports programs.


[Movie]  Name of TV show/series or movie: “15 minutes”.


[Phone]  The emergency telephone numbers dialing within Morocco are 15 and and 19.


[Phone]  The emergency telephone number dialing within Tahiti, French Polynesia.


[Science]  Prefix: Peta- = 1015.



American system

British system















[Tech.]  The HD-DVD will have memory capacity of 15, 30 or 50 GB (gigabytes).  (Toshiba's HD-DVD discs have 30 GB. Sony's Blu-Ray DVD discs have 50 GB.)


[Tech.]  The powers of commercial incandescent light bulbs: 300W, 100W, 75W, 60W, 40W, 30W, 15W, 7.5W and 3W.


[Tech.]  E-85, a kind of fuel for the alternative fuel vehicles, is a blend of 85% ethanol and 15% gasoline.


[Trivia]  Popular U.S. city street speed limits: 15, 25, 30, 35, 40, 45 or 50 miles/hour. 


[Trivia]  The 15th wedding anniversary is traditionally named crystal (or glass) anniversary. Modernly, it may be replaced by watches (or ruby).


[Trivia]  The population of a U.S. town: Lobo, Texas, as of 2005.


[World]  The number of members of the United Nations Security Council: 5 permanent members (China, France, Russian Federation, United Kingdom and United States) and 10 members elected by the General Assembly for two-year terms.


[Zip]  The values of the US non-denominated first-class postage stamps and later values, for the first ounce, starting 14 September 1975 at 10¢ to 44¢, in May 2009.  

















Value (¢)



















[Measure]  The number of gallons in a keg is 15.5.


14 & 15

[History]  The 15th U.S. President: James Buchanan (Democrat, Pennsylvania, 1857-1861).

His Vice President, John Cabell Breckinridge (Kentucky), was the 14th U.S. Vice President.


15 & 16

[History]  The 16th U.S. President: Abraham Lincoln (Republican, Kentucky, 1861-1865).

His Vice Presidents were: Hannibal Hamlin (Maine, 1861-1865), 15th U.S. Vice President and Andrew Johnson (North Carolina, 1865), the 16th U.S. Vice President.