139 (one hundred [and] thirty-nine) is the natural number following 138 and preceding 140.

139 is the 34th prime number. It is a twin prime with 137. Because 141 is a semiprime, 139 is a Chen prime. 139 is the smallest prime before a prime gap of length 10.^[1]

This number is the sum of five consecutive prime numbers (19 + 23 + 29 + 31 + 37).

It is the smallest factor of 64079 which is the smallest Lucas number with prime index which is not prime. It is also the smallest factor of the first nine terms of the Euclid–Mullin sequence, making it the tenth term.

139 is a happy number^[2] and a strictly non-palindromic number.^[3]

• RUM-139 VL-ASROC is a United States Navy ASROC anti-submarine missile
• USS Agent (AM-139) was a United States Navy Admirable-class minesweeper during World War II
• USS Broadwater (APA-139) was a United States Navy Haskell-class attack transport during World War II
• USS Farquhar (DE-139) was a United States Navy destroyer during World War II
• USS General R. E. Callan (AP-139) was a United States Navy transport ship during World War I and World War II
• USS Octorara (IX-139) was a tanker loaned to the Soviet Union during World War II, then returned to the United States in 1944
• USS Pavo (AK-139) was a United States Navy cargo ship during World War II
• USS Salem (CA-139) was a United States Navy Des Moines-class heavy cruiser following World War II
• USS Ward (DD-139) was a United States Navy Wickes-class destroyer during World War II

• British Rail Class 139 is the TOPS classification assigned to the lightweight railcars by West Midlands Trains on the Stourbridge Town Branch Line
• Fiat M139 platform is the next-generation premium rear wheel drive automobile platform from Fiat
• London Buses route 139 is a Transport for London contracted bus route in London

139 is also:

• The year AD 139 or 139 BC
• 139 AH is a year in the Islamic calendar that corresponds to 756 – 757 CE.
• 139 Juewa is a large and dark main belt asteroid discovered in 1874
• The atomic number of untriennium, an unsynthesized chemical element
• Gull Lake No. 139 is a rural municipality in Saskatchewan, Canada
• Sonnet 139 by William Shakespeare
• 139 Rb Gahhie is a village in Chak Jhumra Tehsil in the Punjab province of Pakistan
• Miss 139 was a 1921 film starring Diana Allen and Marc McDermott
• Motorola C139 model cellphone

• List of highways numbered 139
• M139 (disambiguation)
• United Nations Security Council Resolution 139
• United States Supreme Court cases, Volume 139