25,400
25,400 is the number of micrometres in an inch, exactly.
- Even
- Composite
Where 25,400 fits
Why 25,400 is special
Exact rather than measured: the international yard and pound agreement of 1959 defined the inch as precisely 25.4 millimetres, ending a period when the American and British inches differed by about two parts in a million. That sounds negligible and was not — it mattered for interchangeable machined parts.
25,400 is part of
Factors & digit properties
- Divisors (24)
- 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 127, 200, 254, 508, 635, 1016, 1270, 2540, 3175, 5080, 6350, 12700, 25400
- Prime factorisation
- 2^3 × 5^2 × 127
- Digit sum
- 11
- Digital root
- 2
Representations
- Decimal
- 25400
- Scientific notation
- 2.540 × 10^4
Roman numerals
Roman numerals as modelled here goes up to 3,999.
Binary
1 1 0 0 0 1 1 0 0 1 1 1 0 0 0
1 × 16,384 + 1 × 8,192 + 0 × 4,096 + 0 × 2,048 + 0 × 1,024 + 1 × 512 + 1 × 256 + 0 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 0 × 1 = 25,400
Octal
6 1 4 7 0
6 × 4,096 + 1 × 512 + 4 × 64 + 7 × 8 + 0 × 1 = 25,400
Hexadecimal
6 3 3 8
6 × 4,096 + 3 × 256 + 3 × 16 + 8 × 1 = 25,400
Read as powers of two: 16,384 + 8,192 + 512 + 256 + 32 + 16 + 8 = 25,400.
In historical numeral systems
Egyptian
2 fingers, 5 lotuses, 4 coils of rope
2 × 10,000 + 5 × 1,000 + 4 × 100 = 25,400. 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
Related numbers & connections
25400 appears in Numbers in measurement, the topic covering numbers that carry a documented measurement fact.
Numbers Around Us
- appears inUnits and measurement
why?
Strength 0.50, confidence "high".
Science
There are 25,400 micrometres in an inch. Exact by agreement rather than by measurement. Before 1959 the American and British inches differed by about two parts in a million, which is negligible until parts machined in one country have to fit parts machined in the other.
DocumentedScienceGeography: worldwide
Common questions
Is 25,400 a prime number?
No, 25,400 is not prime.
What are the factors of 25,400?
The factors of 25,400 are 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 127, 200, 254, 508, 635, 1016, 1270, 2540, 3175, 5080, 6350, 12700, 25400.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 15 July 2026