51
51 is the atomic number of antimony, and the number in 'Area 51', the secretive US Air Force facility in Nevada.
- Odd
- Composite
Where 51 fits
Why 51 is special
51's cultural fame comes entirely from Area 51's decades of conspiracy-theory notoriety, not from any mathematical property (it factors quietly as 3 × 17).
Same number, different meanings
How 51 is understood across different contexts — never implying one meaning because of another.
- Mathematics
51's cultural fame comes entirely from Area 51's decades of conspiracy-theory notoriety, not from any mathematical property (it factors quietly as 3 × 17).
- Science
51 is the atomic number of antimony.
- Culture
'Area 51' is a secretive United States Air Force facility in Nevada whose name — from its map grid designation — has made it a long-running subject of public fascination and conspiracy theories.
Factors & digit properties
- Divisors (4)
- 1, 3, 17, 51
- Prime factorisation
- 3 × 17
- Digit sum
- 6
- Digital root
- 6
Representations
- Decimal
- 51
- Binary
- 110011
- Octal
- 63
- Hexadecimal
- 33
- Roman numeral
- LI
- Scientific notation
- 5.100 × 10^1
Other mathematical patterns
- Deficient number
- Pentagonal number
- Semiprime
- Lucky number (mathematical sieve)
Related numbers & connections
17 is a factor of 51 (17 × 3 = 51).
View 17 →Mathematically related
- has factor17
why?
Strength 0.50, confidence "high".
Science
51 is the atomic number of antimony.
DocumentedScience
Culture
'Area 51' is a secretive United States Air Force facility in Nevada whose name — from its map grid designation — has made it a long-running subject of public fascination and conspiracy theories.
Widely documentedCultureGeography: United States
Common questions
Is 51 a prime number?
No, 51 is not prime.
What are the factors of 51?
The factors of 51 are 1, 3, 17, 51.
What is 51 in Roman numerals?
51 in Roman numerals is LI.
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