729
729 is both 3 to the sixth power and 27 squared.
Where 729 fits
Why 729 is special
It is one of the few numbers that is simultaneously a perfect square and a perfect cube below a thousand — the others being 1 and 64. Numbers with that property are sixth powers, which is a small and rapidly thinning set.
729 is part of
Factors & digit properties
- Divisors (7)
- 1, 3, 9, 27, 81, 243, 729
- Prime factorisation
- 3^6
- Digit sum
- 18
- Digital root
- 9
Representations
- Decimal
- 729
- Binary
- 1011011001
- Octal
- 1331
- Hexadecimal
- 2d9
- Roman numeral
- DCCXXIX
- Scientific notation
- 7.290 × 10^2
Other mathematical patterns
- Deficient number
- Powerful number
- Lucky number (mathematical sieve)
Related numbers & connections
Both are sixth powers and therefore both square and cube — 64 is 2 to the sixth and 729 is 3 to the sixth. Only 1, 64 and 729 have the property below a thousand.
View 64 →Mathematically related
- has multiple64
why?
Strength 0.50, confidence "high".
Mathematics
A number that is both a square and a cube must be a sixth power, so below a thousand there are only 1, 64 and 729. The scarcity is why such numbers turn up as puzzle answers far more often than their frequency would suggest.
DocumentedMathematics
Common questions
Is 729 a prime number?
No, 729 is not prime.
What are the factors of 729?
The factors of 729 are 1, 3, 9, 27, 81, 243, 729.
What is 729 in Roman numerals?
729 in Roman numerals is DCCXXIX.
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