Question: During the six Apollo spaceflights, how many men walked on the Moon?
About the article "NASA", section "Project Apollo (1961–72)".

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The Apollo program, also known as Project Apollo, was the third human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), the United States' civilian space agency, and the program was responsible for the landing of the first humans on Earth's Moon in 1969.
First conceived during the Presidency of Dwight D. Eisenhower as a three-man spacecraft to follow the one-man Project Mercury which put the first Americans in space, Apollo was later dedicated to President John F. Kennedy's national goal of "landing a man on the Moon and returning him safely to the Earth" by the end of the 1960s, which he proposed in a May 25, 1961, address to Congress.
Project Mercury was followed by the two-man Project Gemini (1962–66).
The first manned flight of Apollo was in 1968.
Kennedy's goal was accomplished on the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Lunar Module (LM) on the Moon on July 20, 1969, and walked on its surface while Michael Collins remained in lunar orbit in the command spacecraft, and all three landed safely on Earth on July 24.
Five subsequent Apollo missions also landed astronauts on the Moon, the last in December 1972.
In these six spaceflights, 12 men walked on the Moon.
Apollo ran from 1961 to 1972, and was supported by the two-man Gemini program which ran concurrently with it from 1962 to 1966.
Gemini missions developed some of the space travel techniques that were necessary for the success of the Apollo missions.
Apollo used Saturn family rockets as launch vehicles.
Apollo / Saturn vehicles were also used for an Apollo Applications Program which consisted of three Skylab space station missions in 1973–74.
Apollo succeeded in achieving its goal of manned lunar landing, despite the major setback of a 1967 Apollo 1 cabin fire that killed the entire crew during a pre-launch test.
After the first landing, sufficient flight hardware remained for nine follow-on landings with an ambitious plan for extended lunar geological and astrophysical exploration.
Budget cuts forced the cancellation of three of these.
Five of the remaining six missions achieved successful landings, but the Apollo 13 landing was prevented by an oxygen tank explosion in transit to the Moon, which disabled the command spacecraft's propulsion and life support.
The crew returned to Earth safely by using the Lunar Module as a "lifeboat" for these functions.
Apollo set several major human spaceflight milestones.
It stands alone in sending manned missions beyond low Earth orbit; Apollo 8 was the first manned spacecraft to orbit another celestial body, while the final Apollo 17 mission marked the sixth Moon landing and the ninth manned mission beyond low Earth orbit.
The program returned of lunar rocks and soil to Earth, greatly contributing to the understanding of the Moon's composition and geological history.
The program laid the foundation for NASA's current human spaceflight capability, and funded construction of its Johnson Space Center and Kennedy Space Center.
Apollo also spurred advances in many areas of technology incidental to rocketry and manned spaceflight, including avionics, telecommunications, and computers. 
Project Apollo (1961–72).
The U.S public's perception of the Soviet lead in putting the first man in space, motivated President John F. Kennedy to ask the Congress on May 25, 1961 to commit the federal government to a program to land a man on the Moon by the end of the 1960s, which effectively launched the Apollo program.
Apollo was one of the most expensive American scientific programs ever.
It is estimated to have cost $ in present-day US dollars.
(In comparison, the Manhattan Project cost roughly $, accounting for inflation.
)It used the Saturn rockets as launch vehicles, which were far bigger than the rockets built for previous projects.
The spacecraft was also bigger; it had two main parts, the combined command and service module (CSM) and the lunar landing module (LM).
The LM was to be left on the Moon and only the command module (CM) containing the three astronauts would eventually return to Earth.
The second manned mission, Apollo 8, brought astronauts for the first time in a flight around the Moon in December 1968.
Shortly before, the Soviets had sent an unmanned spacecraft around the Moon.
On the next two missions docking maneuvers that were needed for the Moon landing were practiced and then finally the Moon landing was made on the Apollo 11 mission in July 1969.
The first person to stand on the Moon was Neil Armstrong, who was followed by Buzz Aldrin, while Michael Collins orbited above.
Five subsequent Apollo missions also landed astronauts on the Moon, the last in December 1972.
Throughout these six Apollo spaceflights, twelve men walked on the Moon.
These missions returned a wealth of scientific data and of lunar samples.
Topics covered by experiments performed included soil mechanics, meteoroids, seismology, heat flow, lunar ranging, magnetic fields, and solar wind.
The Moon landing marked the end of the space race and as a gesture, Armstrong mentioned mankind when he stepped down on the Moon.
Apollo set major milestones in human spaceflight.
It stands alone in sending manned missions beyond low Earth orbit, and landing humans on another celestial body.
Apollo 8 was the first manned spacecraft to orbit another celestial body, while Apollo 17 marked the last moonwalk and the last manned mission beyond low Earth orbit.
The program spurred advances in many areas of technology peripheral to rocketry and manned spaceflight, including avionics, telecommunications, and computers.
Apollo sparked interest in many fields of engineering and left many physical facilities and machines developed for the program as landmarks.
Many objects and artifacts from the program are on display at various locations throughout the world, notably at the Smithsonian's Air and Space Museums.
First human spaceflights.
The first human spaceflight took place on 12 April 1961, when cosmonaut Yuri Gagarin made one orbit around the Earth aboard the Vostok 1 spacecraft, launched by the Soviet space program.
Valentina Tereshkova became the first woman in space aboard Vostok 6 on 16 June 1963.
Both spacecraft were launched by Vostok 3KA launch vehicles.
Alexei Leonov made the first spacewalk when he left Voskhod 2 on 8 March 1965.
Svetlana Savitskaya became the first woman to do so on 25 July 1984.
The United States became the second nation to achieve manned spaceflight with the suborbital flight of astronaut Alan Shepard aboard "Freedom 7" as part of Project Mercury.
The spacecraft was launched on 5 May 1961 on a Redstone rocket.
The first U.S. orbital flight was that of John Glenn aboard "Friendship 7", launched 20 February 1962 on an Atlas rocket.
From 1981 to 2011, the U.S. conducted all its human spaceflight missions with reusable space shuttles.
Sally Ride became the first American woman in space in 1983.
Eileen Collins was the first female shuttle pilot, and with shuttle mission STS-93 in 1999 she became the first woman to command a U.S. spacecraft.
China became the third nation to achieve human spaceflight when Yang Liwei launched into space on a Chinese-made vehicle, the Shenzhou 5, on 15 October 2003.
The flight also made China the third nation to have launched its own manned spacecraft using its own launcher.
The first Chinese woman, Liu Yang, was launched in June 2012 aboard Shenzhou 9.
Previous European (Hermes) and Japanese (HOPE-X) domestic manned programs were abandoned after years of development, as was the first Chinese attempt, the Shuguang spacecraft.
The farthest destination for a human spaceflight mission has been the Moon.
The only manned missions to the Moon have been those conducted by NASA as part of the Apollo program.
The first such mission, Apollo 8, orbited the Moon but did not land.
The first Moon landing mission was Apollo 11, during which—on 20 July 1969—Neil Armstrong and Buzz Aldrin became the first people to set foot on the Moon.
Six missions landed in total, numbered Apollo 11–17, excluding Apollo 13.
Altogether 12 men walked on the Moon, the only humans to have been on an extraterrestrial body.
The Soviet Union discontinued its program for lunar orbiting and landing of human spaceflight missions in 1974 when Valentin Glushko became General Designer of NPO Energiya.
The longest single human spaceflight is that of Valeriy Polyakov, who left Earth on 8 January 1994, and did not return until 22 March 1995 (a total of 437 days 17 hr.
58 min.
16 sec.).
Sergei Krikalyov has spent the most time of anyone in space, 803 days, 9 hours, and 39 seconds altogether.
The longest period of continuous human presence in space is on the International Space Station, exceeding the previous record of almost 10 years (or 3,634 days) held by Mir, spanning the launch of Soyuz TM-8 on 5 September 1989 to the landing of Soyuz TM-29 on 28 August 1999.
For many years beginning in 1961, only two countries, the USSR (later Russia) and the United States, had their own astronauts.
Citizens of other nations flew in space, beginning with the flight of Vladimir Remek, a Czech, on a Soviet spacecraft on 2 March 1978. , citizens from 38 nations (including space tourists) have flown in space aboard Soviet, American, Russian, and Chinese spacecraft. 
 Eugene Cernan, the last man who walked on the moon during the Apollo 17 mission Roger Clemens, former pitcher for the Houston Astros  
The Wonder of It All is a 2007 documentary directed by Jeffrey Roth and distributed by Indican Pictures.
It is composed of first-person interviews with six of the Apollo astronauts who walked on the moon.
The astronauts explain their backgrounds, their moon missions, and how walking on the moon changed their lives.