1,089
1,089 is the result of a digit-reversal trick that works on almost every three-digit number.
Where 1,089 fits
Why 1,089 is special
Take any three-digit number whose first and last digits differ by at least two, reverse it, subtract the smaller from the larger, then add that result to its own reverse. The answer is 1,089 every time. The trick is a staple of recreational mathematics because the algebra behind it is simple enough to show a child yet the result feels like sleight of hand.
1,089 is part of
Factors & digit properties
- Divisors (9)
- 1, 3, 9, 11, 33, 99, 121, 363, 1089
- Prime factorisation
- 3^2 × 11^2
- Digit sum
- 18
- Digital root
- 9
Representations
- Decimal
- 1089
- Binary
- 10001000001
- Octal
- 2101
- Hexadecimal
- 441
- Roman numeral
- MLXXXIX
- Scientific notation
- 1.089 × 10^3
Other mathematical patterns
- Deficient number
- Powerful number
Related numbers & connections
Both are digit-reversal curiosities. 1089 always works and is a parlour trick; 196 has resisted a billion digits of computation and is an open problem.
View 196 →Other connections
- contrasts with196
why?
Strength 0.50, confidence "high".
Mathematics
Write the three-digit number as 100a + 10b + c. Subtracting its reverse gives 99(a − c), which for any difference of at least two is one of 198, 297, 396, 495, 594, 693, 792 or 891 — and every one of those, added to its own reverse, is 1,089. The trick is exhaustive rather than mysterious.
DocumentedMathematics
Common questions
Is 1,089 a prime number?
No, 1,089 is not prime.
What are the factors of 1,089?
The factors of 1,089 are 1, 3, 9, 11, 33, 99, 121, 363, 1089.
What is 1,089 in Roman numerals?
1,089 in Roman numerals is MLXXXIX.
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