400
400 metres is one lap of a standard outdoor running track, and 400 is a perfect square (20²).
Where 400 fits
Why 400 is special
400 is the number that defines the shape of athletics: a standard outdoor track measures 400 m in lane 1, which makes it the reference distance every other track event is built around — 800 m is two laps, 1500 m is nearly four. It is also cleanly 20².
400 is part of
Factors & digit properties
- Divisors (15)
- 1, 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, 80, 100, 200, 400
- Prime factorisation
- 2^4 × 5^2
- Digit sum
- 4
- Digital root
- 4
Representations
- Decimal
- 400
- Binary
- 110010000
- Octal
- 620
- Hexadecimal
- 190
- Roman numeral
- CD
- Scientific notation
- 4.000 × 10^2
Other mathematical patterns
- Abundant number
- Powerful number
- Harshad (Niven) number
Related numbers & connections
400 is the square of 20 (20² = 400).
View 20 →400 metres is one lane-1 lap of a standard outdoor athletics track.
Mathematically related
- is the square of20
why?
Strength 0.50, confidence "high".
Numbers Around Us
- appears inStandard athletics track lap distance
why?
Strength 0.50, confidence "high".
Sport
A standard outdoor athletics track measures 400 metres in lane 1, making it the reference distance from which other track events are derived — 800 m is two laps and the 4 × 400 m relay one lap per runner.
DocumentedSportGeography: athletics (international)
Mathematics
400 is a perfect square: 20² = 400.
DocumentedMathematics
Common questions
Is 400 a prime number?
No, 400 is not prime.
What are the factors of 400?
The factors of 400 are 1, 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, 80, 100, 200, 400.
What is 400 in Roman numerals?
400 in Roman numerals is CD.
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: 30 July 2026