181 (number)

In mathematics

181 is an odd number

181 is a centered number

181 is a centered pentagonal number

181 is a centered 12-gonal number

181 is a centered 18-gonal number

181 is a centered 30-gonal number

181 is a centered square number

181 is a star number that represents a centered hexagram (as in the game of Chinese checkers)

181 is a deficient number, as 1 is less than 181

181 is an odious number

181 is a prime number

181 is a Chen prime

181 is a dihedral prime

181 is a full reptend prime

181 is a palindromic prime

181 is a strobogrammatic prime, the same when viewed upside down

181 is a twin prime with 179

181 is a square-free number

181 is an undulating number, if written in the ternary, the negaternary, or the nonary numeral systems

181 is the difference of 2 square numbers: 91² – 90²

181 is the sum of 2 consecutive square numbers: 9² + 10²

181 is the sum of 5 consecutive prime numbers: 29 + 31 + 37 + 41 + 43

In geography

Langenburg No. 181, Saskatchewan rural municipality in Saskatchewan, Canada

181 Fremont Street proposed skyscraper in San Francisco, California

181 West Madison Street, Chicago

In the military

181st (Brandon) Battalion, CEF was a unit in the Canadian Expeditionary Force during World War I

181st Airlift Squadron is a unit of the Texas Air National Guard

181st Infantry Brigade of the United States Army based at Fort McCoy, Wisconsin

181st Intelligence Wing is a unit of the United States Air Force located at Hulman Field, Terre Haute, Indiana

AN/APQ-181 an all-weather, low probability of intercept (LPI) radar system for the U.S. Air Force B-2A Spirit bomber aircraft

Bücker Bü 181 Bestmann single-engine trainer aircraft during World War II

USNS Adelphi (T-AG-181) was a ship scheduled to be acquired by the U.S. Navy, however, the program was cancelled

USNS Fred C. Ainsworth (T-AP-181) was a United States Navy troop transport during World War II

USNS Potomac (T-AO-181) was a United States Navy Oiler following the Vietnam War

USS Accokeek (ATA-181) was a United States Navy ATA-174 class auxiliary ocean tugboat during World War II

USS Flagler (AK-181) was a United States Navy Alamosa-class cargo ship following World War II

USS Hopewell (DD-181) was a United States Navy Wickes class destroyer following World War I

USS Pompano (SS-181) was a United States Navy Porpoise-class submarine during World War II

USS Straub (DE-181) was a United States Navy Cannon-class destroyer escort during World War II

In movies

“181: Fragments of a Journey in Palestine-Israel,” winner of the 2005 Yamagata International Documentary Film Festival

The war film “The Enemy Below” revolves around the fictitious Buckley-class destroyer escort, the USS Hayes (DE-181) and a German U-boat

In sports

Retired American Thoroughbred horse racing jockey Randy Romero won a track record 181 races at the Fair Grounds Race Course in New Orleans

In transportation

The Volkswagen 181

Lufthansa Flight 181, which was hijacked on October 13, 1977

London Buses route 181

181 Union City-New York, a New Jersey Transit bus route from New Jersey to New York

The Córas Iompair Éireann CIE 181 Class diesel locomotives, and numbered B181 to B192, built by General Motors Electro-Motive Division (EMD) in 1966

East 181st Avenue, a light rail station on the MAX Blue Line in Gresham, Oregon

New York City Subway stations in Manhattan:

181st Street (IND Eighth Avenue Line), at Fort Washington Avenue served by the A train

181st Street (IRT Broadway – Seventh Avenue Line), at St. Nicholas Avenue served by the 1 train

181st Street (Manhattan)

Oregon Route 229, also known as the Siletz Highway No. 181

In other fields

181 is also:

The year AD 181 or 181 BC

The atomic number of an element temporarily called Unoctunium

181 Eucharis is a large K-type Main belt asteroid

Minuscule 181 (in the Gregory-Aland numbering), α 101 (Soden), is a Greek minuscule manuscript of the New Testament

Mir-181 microRNA precursor is a small non-coding RNA molecule