1,729
1729 is the smallest number expressible as the sum of two positive cubes in two different ways (1³ + 12³ = 9³ + 10³), known as the Hardy–Ramanujan number.
- Odd
- Composite
Where 1,729 fits
Why 1,729 is special
1729 is mathematics' most famous 'dull number' anecdote: G. H. Hardy remarked that the taxicab he arrived in bore an uninteresting number, and Ramanujan immediately replied that 1729 is the smallest number expressible as a sum of two cubes in two different ways. Both decompositions are verifiable — 1³ + 12³ = 1 + 1728, and 9³ + 10³ = 729 + 1000.
Factors & digit properties
- Divisors (8)
- 1, 7, 13, 19, 91, 133, 247, 1729
- Prime factorisation
- 7 × 13 × 19
- Digit sum
- 19
- Digital root
- 1
Representations
- Decimal
- 1729
- Binary
- 11011000001
- Octal
- 3301
- Hexadecimal
- 6c1
- Roman numeral
- MDCCXXIX
- Scientific notation
- 1.729 × 10^3
Other mathematical patterns
- Deficient number
- Harshad (Niven) number
Related numbers & connections
1729 factors as 7 × 13 × 19, so it is a multiple of 13.
View 13 →Mathematically related
- has multiple13
why?
Strength 0.50, confidence "high".
History
1729 is known as the Hardy–Ramanujan number after G. H. Hardy's published account of remarking that his taxicab's number seemed dull, to which Srinivasa Ramanujan replied that it was the smallest number expressible as a sum of two cubes in two different ways.
DocumentedHistoryPeriod: early 20th century
Mathematics
1729 is the smallest number expressible as the sum of two positive cubes in two distinct ways: 1³ + 12³ = 9³ + 10³ = 1729. It is the first of the 'taxicab numbers'.
DocumentedMathematics
Common questions
Is 1,729 a prime number?
No, 1,729 is not prime.
What are the factors of 1,729?
The factors of 1,729 are 1, 7, 13, 19, 91, 133, 247, 1729.
What is 1,729 in Roman numerals?
1,729 in Roman numerals is MDCCXXIX.
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: 30 July 2026