145 (one hundred [and] forty-five) is the natural number following 144 and preceding 146.

• Although composite, 145 is a Fermat pseudoprime in sixteen bases with b < 145. In four of those bases, it is a strong pseudoprime: 1, 12, 17, and 144.
• the Mertens function returns 0.^[1]
• 145 is a pentagonal number^[2] and a centered square number.^[3]
• ${\displaystyle 145=12^{2}+1^{2}=8^{2}+9^{2}}$. 145 is the fourth number that is the sum of two different pairs of squares. Also, 145 is the result of 3⁴ + 4³, making it a Leyland number.
• ${\displaystyle 145=1!+4!+5!}$, making it a factorion.^[4] The only other numbers that have this property are 1, 2 and 40585.^[4]
• ${\displaystyle 145=5^{2}+5!=11^{2}+4!=12^{2}+1!}$, making 145 the smallest number that can be written as the sum of a square number and a factorial in 3 ways. The next number with this property is 46249.^[5]

• USS Armada (AM-145) was a United States Navy Admirable-class minesweeper during World War II
• USS Colbert (APA-145) was a United States Navy Haskell-class attack transport during World War II
• USS General Harry Taylor (AP-145) was a United States Navy General G. O. Squier-class transport during World War II
• USS Greer (DD-145) was a United States Navy Wickes-class destroyer during World War II
• USS Huse (DE-145) was a United States Navy Edsall-class destroyer escort during World War II
• USS Roanoke (CL-145) was a United States Navy Worcester-class cruiser following World War II

• The Grand Union Canal Race is a 145-mile ultramarathon from Birmingham to London along the Grand Union Canal

• Eurocopter EC 145 is a twin-engine light utility helicopter
• The Delahaye 145 Sports Car from 1938^[6]
• The Alfa Romeo 145 car produced between 1994 and 2001
• Volvo 145 Express station wagon
• ERJ 145 regional jets produced by Embraer
• Golden Gate Transit Bus Route 145^[7]
• London Bus Route 145^[8]

145 is also:

• The year AD 145 or 145 BC
• 145 AH is a year in the Islamic calendar that corresponds to 762 – 763 CE
• 145 Adeona is a large main belt asteroid
• Psalm 145
• Sonnet 145
• Apple Computer laptops, such as the PowerBook 145 and PowerBook 145B
• Puff Daddy song “Picture it” includes the lyrics “in something foreign soarin’ 145”
• Tsuu T'ina Nation 145 Indian reserve in Alberta, Canada
• 145 mg medicine tablets, as with Tricor
• "One Four Five" is a song by The Cat Empire

• List of highways numbered 145
• United Nations Security Council Resolution 145
• United States Supreme Court cases, Volume 145