384,400
The Moon is about 384,400 km from Earth on average.
Where 384,400 fits
Why 384,400 is special
The distance is known to within centimetres because Apollo and Soviet missions left retroreflectors on the surface that lasers are still bounced off today. Those measurements show the Moon receding by about 3.8 cm a year.
Same number, different meanings
How 384,400 is understood across different contexts — never implying one meaning because of another.
- Mathematics
The distance is known to within centimetres because Apollo and Soviet missions left retroreflectors on the surface that lasers are still bounced off today. Those measurements show the Moon receding by about 3.8 cm a year.
- History
Apollo 11 left a panel of corner-cube reflectors on the Moon in 1969, and Apollo 14 and 15 and two Soviet Lunokhod rovers added more. Observatories have been bouncing lasers off them ever since, which is why the distance is known to centimetres rather than kilometres. The same measurements show the Moon receding by about 3.8 centimetres a year, so the figure is not a constant but a slowly rising one.
- Science
The Moon's average distance is about 384,400 km, known precisely because Apollo and Soviet missions left retroreflectors that lasers are still bounced off. Those measurements show the Moon receding by roughly 3.8 cm each year.
384,400 is part of
Factors & digit properties
- Divisors (45)
- 1, 2, 4, 5, 8, 10, 16, 20, 25, 31, 40, 50, 62, 80, 100, 124, 155, 200, 248, 310, 400, 496, 620, 775, 961, 1240, 1550, 1922, 2480, 3100, 3844, 4805, 6200, 7688, 9610, 12400, 15376, 19220, 24025, 38440, 48050, 76880, 96100, 192200, 384400
- Prime factorisation
- 2^4 × 5^2 × 31^2
- Digit sum
- 19
- Digital root
- 1
Representations
- Decimal
- 384400
- Scientific notation
- 3.844 × 10^5
Roman numerals
Roman numerals as modelled here goes up to 3,999.
Binary
1 0 1 1 1 0 1 1 1 0 1 1 0 0 1 0 0 0 0
1 × 262,144 + 0 × 131,072 + 1 × 65,536 + 1 × 32,768 + 1 × 16,384 + 0 × 8,192 + 1 × 4,096 + 1 × 2,048 + 1 × 1,024 + 0 × 512 + 1 × 256 + 1 × 128 + 0 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 0 × 2 + 0 × 1 = 384,400
Octal
1 3 5 6 6 2 0
1 × 262,144 + 3 × 32,768 + 5 × 4,096 + 6 × 512 + 6 × 64 + 2 × 8 + 0 × 1 = 384,400
Hexadecimal
5 d d 9 0
5 × 65,536 + d × 4,096 + d × 256 + 9 × 16 + 0 × 1 = 384,400
Read as powers of two: 262,144 + 65,536 + 32,768 + 16,384 + 4,096 + 2,048 + 1,024 + 256 + 128 + 16 = 384,400.
In historical numeral systems
Egyptian
3 tadpoles, 8 fingers, 4 lotuses, 4 coils of rope
3 × 100,000 + 8 × 10,000 + 4 × 1,000 + 4 × 100 = 384,400. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Abundant number
- Powerful number
Related numbers & connections
The Sun's diameter is over three times the Earth–Moon distance, so the entire lunar orbit would fit inside the Sun with room to spare.
View 1392700 →The Sun is about 390 times further away than the Moon and about 400 times wider, which is why the two appear almost the same size and why total eclipses work.
View 150 →History
Apollo 11 left a panel of corner-cube reflectors on the Moon in 1969, and Apollo 14 and 15 and two Soviet Lunokhod rovers added more. Observatories have been bouncing lasers off them ever since, which is why the distance is known to centimetres rather than kilometres. The same measurements show the Moon receding by about 3.8 centimetres a year, so the figure is not a constant but a slowly rising one.
DocumentedHistoryPeriod: 1969 onwards
Science
The Moon's average distance is about 384,400 km, known precisely because Apollo and Soviet missions left retroreflectors that lasers are still bounced off. Those measurements show the Moon receding by roughly 3.8 cm each year.
DocumentedScience
Common questions
Is 384,400 a prime number?
No, 384,400 is not prime.
What are the factors of 384,400?
The factors of 384,400 are 1, 2, 4, 5, 8, 10, 16, 20, 25, 31, 40, 50, 62, 80, 100, 124, 155, 200, 248, 310, 400, 496, 620, 775, 961, 1240, 1550, 1922, 2480, 3100, 3844, 4805, 6200, 7688, 9610, 12400, 15376, 19220, 24025, 38440, 48050, 76880, 96100, 192200, 384400.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026