133
E133 is Brilliant Blue FCF.
- Odd
- Composite
Where 133 fits
Why 133 is special
It was banned in several European countries for decades while being permitted in the United States, and the positions later reversed in part.
Same number, different meanings
How 133 is understood across different contexts — never implying one meaning because of another.
- Mathematics
It was banned in several European countries for decades while being permitted in the United States, and the positions later reversed in part.
- Science
The SI second is defined as 9,192,631,770 periods of a specific transition in caesium-133. The definition moved timekeeping off astronomy in 1967, so a second is now fixed by atomic physics rather than by the Earth's rotation.
- Everyday life
E133 Brilliant Blue FCF is a synthetic triarylmethane dye. National bans in several European states preceded EU-wide authorisation, an inversion of the usual pattern with United States approval.
133 is part of
Factors & digit properties
- Divisors (4)
- 1, 7, 19, 133
- Prime factorisation
- 7 × 19
- Digit sum
- 7
- Digital root
- 7
Representations
- Decimal
- 133
- Binary
- 10000101
- Octal
- 205
- Hexadecimal
- 85
- Roman numeral
- CXXXIII
- Scientific notation
- 1.330 × 10^2
Other mathematical patterns
- Deficient number
- Happy number
- Semiprime
- Harshad (Niven) number
- Lucky number (mathematical sieve)
Related numbers & connections
The SI second is defined by 9,192,631,770 periods of a transition in caesium-133, which moved timekeeping off astronomy in 1967.
Defining the second by caesium-133 fixed the unit that sixty of them make a minute.
View 60 →Science
The SI second is defined as 9,192,631,770 periods of a specific transition in caesium-133. The definition moved timekeeping off astronomy in 1967, so a second is now fixed by atomic physics rather than by the Earth's rotation.
DocumentedScienceGeography: International — BIPMPeriod: 1967–
Everyday life
E133 Brilliant Blue FCF is a synthetic triarylmethane dye. National bans in several European states preceded EU-wide authorisation, an inversion of the usual pattern with United States approval.
DocumentedEveryday lifeGeography: European Union and states adopting the E number systemPeriod: 1962–
Common questions
Is 133 a prime number?
No, 133 is not prime.
What are the factors of 133?
The factors of 133 are 1, 7, 19, 133.
What is 133 in Roman numerals?
133 in Roman numerals is CXXXIII.
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: 3 August 2026