161 (number)

161 (one hundred [and] sixty-one) is the natural number following 160 and preceding 162.

In mathematics

 * 161 is the sum of five consecutive prime numbers: 23, 29, 31, 37, and 41
 * 161 is a hexagonal pyramidal number.
 * 161 is a semiprime. Since its prime factors 7 and 23 are both Gaussian primes, 161 is a Blum integer.
 * 161 is a palindromic number
 * $161⁄72$ is a commonly used rational approximation of the square root of 5 and is the closest fraction with denominator <300 to that number.

In the military

 * USNS Lone Jack (T-AO-161) was a U.S. Navy Type T2 tanker during World War II
 * USS Barber (DE-161) was a U.S. Navy Buckley-class destroyer escort during World War II
 * USS Barite (IX-161) was a U.S. Navy Trefoil-class concrete barge during World War II
 * USS Beaverhead (AK-161) was a U.S. Navy Alamosa-class cargo ship during World War II
 * USS Climax (AM-161) was a U.S. Navy Admirable-class minesweeper during World War II
 * USS Dickens (APA-161) was a U.S. Navy Haskell-class attack transport during World War II
 * USS Narada (SP-161) was a U.S. Navy wooden yacht during World War I
 * USS Palmer (DD-161) was a U.S. Navy Wickes-class destroyer during World War II
 * USS Salinan (ATF-161) was a U.S. Navy Achomawi-class fleet ocean tug following World War II
 * USS S-50 (SS-161) was a U.S. Navy fourth-group S-class submarine between 1920 and 1931
 * USS Stingray (SS-161) is a fictional U.S. Navy diesel engine submarine featured in the 1996 film Down Periscope
 * The 161st Intelligence Squadron unit of the Kansas Air National Guard. Its parent unit is the 184th Intelligence Wing

In music

 * The Bose 161 Speaker System (2001)
 * The Kay K-161 ThinTwin guitar
 * The song 161 by Pilz

In transportation

 * MTA Maryland commuter bus 161
 * New Jersey Bus Route 161
 * London Bus route 161

In other fields
161 is also:
 * The year AD 161 or 161 BC
 * 161 AH is a year in the Islamic calendar that corresponds to 777 – 778 CE
 * 161 Athor is an M-type Main belt asteroid
 * E.161 is an ITU-T assigns letters to the 12-key telephone keypad
 * Fiorina Fury 161 is a foundry facility and penal colony from the film Alien 3
 * 161 is used by Anti Fascist Action as a code for AFA (A=1, F=6, by order of the alphabet), sometimes used in 161>88 (88 is code for Heil Hitler among neo-nazis, as H=8)