173
E173 is aluminium, used as a surface colour.
- Odd
- Prime
Where 173 fits
Why 173 is special
It is permitted only for external decoration of confectionery, which is a narrower authorisation than most additives carry.
173 is part of
Factors & digit properties
- Divisors (2)
- 1, 173
- Prime factorisation
- 173
- Digit sum
- 11
- Digital root
- 2
Representations
- Decimal
- 173
- Binary
- 10101101
- Octal
- 255
- Hexadecimal
- ad
- Roman numeral
- CLXXIII
- Scientific notation
- 1.730 × 10^2
Other mathematical patterns
- Deficient number
- Sophie Germain prime
Related numbers & connections
Both are metal-based colours whose authorisation is narrower than most additives carry.
View 171 →Other connections
- is associated with171
why?
Strength 0.50, confidence "high".
Everyday life
E173 aluminium is authorised in the European Union only for external coating of sugar confectionery and for decoration of cakes and pastries, not for incorporation into food.
DocumentedEveryday lifeGeography: European Union and states adopting the E number systemPeriod: 1962–
Common questions
Is 173 a prime number?
Yes, 173 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 173?
The factors of 173 are 1, 173.
What is 173 in Roman numerals?
173 in Roman numerals is CLXXIII.
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: 3 August 2026