169 (number) explained

Number:	169
Divisor:	1, 13, 169

169 (one hundred [and] sixty-nine) is the natural number following 168 and preceding 170.

In mathematics

169 is an odd number, a composite number, and a deficient number.

169 is a square number: 13 × 13 = 169, and if each number is reversed the equation is still true: 31 × 31 = 961. 144 shares this property: 12 × 12 = 144, 21 × 21 = 441.

169 is one of the few squares to also be a centered hexagonal number.^[1] Like all odd squares, it is a centered octagonal number. 169 is an odd-indexed Pell number, thus it is also a Markov number, appearing in the solutions (2, 169, 985), (2, 29, 169), (29, 169, 14701), etc. 169 is the sum of seven consecutive primes: 13 + 17 + 19 + 23 + 29 + 31 + 37. 169 is a difference in consecutive cubes, equaling

8 ^{3-7} ^{3.}

In astronomy

• 169 Zelia is a bright main belt asteroid
• Gliese 169 is an orange, main sequence (K7 V) star in the constellation Taurus
• QSO B0307+169 is a quasar in the constellation Aries
• Sayh al Uhaymir 169 is a 206g lunar meteorite found in Sultanate of Oman

In the military

• was a United States Navy technical research ship during the 1960s
• was a United States Navy during World War II
• was a United States Navy during World War II
• was a United States Navy following World War I
• was a United States Navy during World War II
• was a United States Navy submarine during World War II
• 169th Battalion, CEF unit in the Canadian Expeditionary Force during the World War I
• 169th Fires Brigade the US Army National Guard artillery brigade, a part of the Colorado Army National Guard
• The United States Air Force's 169th Fighter Wing fighter unit at McEntire Joint National Guard Station, South Carolina
• 169 or 169th Squadrons
  • 169th Airlift Squadron, a unit of the U.S. Air Force
  • Marine Light Attack Helicopter Squadron 169, United States Marine Corps Light Attack Helicopter Squadron
  • No. 169 Squadron RAF, a unit of the United Kingdom Royal Air Force

In transportation

• Metro Transit Route 169 in Seattle^[2]
• 169th Street station on the IND Queens Boulevard Line of the New York City Subway served by the and trains
• 169th Street was a station on the demolished IRT Third Avenue Line of the New York City Subway

In TV and radio

• The IEC 169-2 connector TV aerial plug

In other fields

169 is also:

• The year AD 169 or 169 BC
• The atomic number of an element temporarily called Unhexennium^[3]
• 169 is the number of nonequivalent starting hands in the card game Texas hold 'em
• 169 is known in the computing world as the first number of an automatic IPv4 address assigned by TCP/IP when no external networking device is contactable
• Minuscule 169 is a Greek minuscule manuscript of the New Testament, on parchment

See also

• List of highways numbered 169
• United States Supreme Court cases, Volume 169
• United Nations Security Council Resolution 169
• St. Joseph Community Consolidated School District 169

External links

• Number Facts and Trivia: 169
• The Positive Integer 169
• Prime curiosities: 169
• The Number 169
• Number Gossip 169

Notes and References

1. Web site: Sloane's A003215 : Hex (or centered hexagonal) numbers. The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. 2016-05-28.
2. Web site: Metro Route 169 Timetable, Weekday . transit.metrokc.gov . 13 January 2022 . https://web.archive.org/web/20021002070149/http://transit.metrokc.gov/tops/bus/schedules/s169_0_.html . 2 October 2002 . dead.
3. Web site: FLW Incorporated | Specialists in Physical Measurement, Testing, Calibration & Control .