343
Sound travels at about 343 metres per second in air at 20 degrees Celsius.
Where 343 fits
Why 343 is special
Speed depends on temperature, not on air pressure or altitude directly, which is why the figure must be quoted with a temperature. It is also why counting the seconds between lightning and thunder gives roughly one kilometre for every three seconds.
Same number, different meanings
How 343 is understood across different contexts — never implying one meaning because of another.
- Mathematics
Speed depends on temperature, not on air pressure or altitude directly, which is why the figure must be quoted with a temperature. It is also why counting the seconds between lightning and thunder gives roughly one kilometre for every three seconds.
- History
The sound barrier is this speed, and it is not fixed: sound travels more slowly in the colder air at altitude, so the speed an aircraft must exceed falls as it climbs. Chuck Yeager passed it in level flight in the Bell X-1 in October 1947 at around 13,000 metres, where the figure is nearer 295 metres per second. Mach number is quoted as a ratio rather than a speed for exactly this reason — the denominator moves.
- Science
The speed of sound in air is about 343 metres per second (dry air at 20 degrees Celsius). It depends on temperature rather than on pressure, rising roughly 0.6 metres per second for every degree — which is why the figure is quoted with a temperature and why sound travels faster on a hot day.
343 is part of
Factors & digit properties
- Divisors (4)
- 1, 7, 49, 343
- Prime factorisation
- 7^3
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 343
- Scientific notation
- 3.430 × 10^2
Roman numerals
C C C X L I I I
CCCXLIII uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 0 1 0 1 0 1 1 1
1 × 256 + 0 × 128 + 1 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 1 × 4 + 1 × 2 + 1 × 1 = 343
Octal
5 2 7
5 × 64 + 2 × 8 + 7 × 1 = 343
Hexadecimal
1 5 7
1 × 256 + 5 × 16 + 7 × 1 = 343
Read as powers of two: 256 + 64 + 16 + 4 + 2 + 1 = 343.
In historical numeral systems
Egyptian
3 coils of rope, 4 hobbles, 3 strokes
3 × 100 + 4 × 10 + 3 × 1 = 343. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
5 vertical wedges (sixties place), 4 corner wedges + 3 vertical wedges (units place)
5 × 60 + 43 = 343. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
tau, then mu, then gamma, marked as a numeral
tau-mu-gamma + keraia
tau + mu + gamma written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
shin, then mem, then gimel
shin-mem-gimel
shin (300) + mem (40) + gimel (3) = 343, written in descending order.
Maya
3 bars + 2 dots (upper, twenties place) over 3 dots (lower, units place)
17 × 20 + 3 = 343. Places stack vertically with the smallest at the bottom, so the upper group is worth twenty times the lower.
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
- Palindromic number
- Deficient number
- Powerful number
Related numbers & connections
343 appears in Numbers in physics, the topic covering numbers that carry a documented physics fact.
Both describe air at defined conditions. The speed of sound depends on temperature rather than pressure directly, which is why 343 m/s must be quoted with a temperature and 1,013 hPa with an altitude.
View 1013 →Numbers Around Us
- appears inPhysics
why?
Strength 0.50, confidence "high".
Other connections
- is associated with1013
why?
Strength 0.50, confidence "high".
History
The sound barrier is this speed, and it is not fixed: sound travels more slowly in the colder air at altitude, so the speed an aircraft must exceed falls as it climbs. Chuck Yeager passed it in level flight in the Bell X-1 in October 1947 at around 13,000 metres, where the figure is nearer 295 metres per second. Mach number is quoted as a ratio rather than a speed for exactly this reason — the denominator moves.
DocumentedHistoryPeriod: 1947
Science
The speed of sound in air is about 343 metres per second (dry air at 20 degrees Celsius). It depends on temperature rather than on pressure, rising roughly 0.6 metres per second for every degree — which is why the figure is quoted with a temperature and why sound travels faster on a hot day.
DocumentedScienceGeography: dry air at 20 degrees CelsiusSound covers about 343 metres per second in air at 20 degrees Celsius, so roughly three seconds between lightning and thunder means about a kilometre. The speed depends on temperature rather than on pressure or altitude directly, which is why the figure is meaningless without one.
DocumentedScience
Common questions
Is 343 a prime number?
No, 343 is not prime.
What are the factors of 343?
The factors of 343 are 1, 7, 49, 343.
What is 343 in Roman numerals?
343 in Roman numerals is CCCXLIII. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be CCCXXXXIII, which Roman inscriptions used freely — the strict subtractive form is a later convention.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 3 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026