45
45 is a triangular number, the atomic number of rhodium, and the standard playback speed (45 RPM) for vinyl singles.
- Odd
- Composite
Where 45 fits
Why 45 is special
45's mathematical identity (triangular, the sum of 1 through 9) sits alongside a real audio-engineering standard still referenced whenever vinyl singles are discussed.
Same number, different meanings
How 45 is understood across different contexts — never implying one meaning because of another.
- Mathematics
45's mathematical identity (triangular, the sum of 1 through 9) sits alongside a real audio-engineering standard still referenced whenever vinyl singles are discussed.
- Science
45 is the atomic number of rhodium.
- Media & popular culture
45 RPM is the standard playback speed for 7-inch vinyl singles, distinct from the slower 33⅓ RPM used for full-length LP albums.
Factors & digit properties
- Divisors (6)
- 1, 3, 5, 9, 15, 45
- Prime factorisation
- 3^2 × 5
- Digit sum
- 9
- Digital root
- 9
Representations
- Decimal
- 45
- Binary
- 101101
- Octal
- 55
- Hexadecimal
- 2d
- Roman numeral
- XLV
- Scientific notation
- 4.500 × 10^1
Other mathematical patterns
- Triangular number
- Deficient number
- Kaprekar number
- Hexagonal number
- Harshad (Niven) number
Related numbers & connections
9 is a factor of 45 (9 × 5 = 45).
View 9 →Science
45 is the atomic number of rhodium.
DocumentedScience
Media & popular culture
45 RPM is the standard playback speed for 7-inch vinyl singles, distinct from the slower 33⅓ RPM used for full-length LP albums.
DocumentedMedia & popular culture
Common questions
Is 45 a prime number?
No, 45 is not prime.
What are the factors of 45?
The factors of 45 are 1, 3, 5, 9, 15, 45.
What is 45 in Roman numerals?
45 in Roman numerals is XLV.
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