78
78 is a triangular number (the sum of 1 through 12) and the atomic number of platinum.
- Even
- Composite
Where 78 fits
Why 78 is special
78's triangular-number identity ties it neatly to the twelve months of the calendar year, purely as a mathematical curiosity.
Factors & digit properties
- Divisors (8)
- 1, 2, 3, 6, 13, 26, 39, 78
- Prime factorisation
- 2 × 3 × 13
- Digit sum
- 15
- Digital root
- 6
Representations
- Decimal
- 78
- Binary
- 1001110
- Octal
- 116
- Hexadecimal
- 4e
- Roman numeral
- LXXVIII
- Scientific notation
- 7.800 × 10^1
Other mathematical patterns
- Triangular number
- Abundant number
Related numbers & connections
39 is a factor of 78 (39 × 2 = 78).
View 39 →Mathematically related
- has factor39
why?
Strength 0.50, confidence "high".
Science
78 is the atomic number of platinum.
DocumentedScience
Mathematics
78 is a triangular number (the sum of 1 through 12) and factors as 2 × 3 × 13.
DocumentedMathematics
Common questions
Is 78 a prime number?
No, 78 is not prime.
What are the factors of 78?
The factors of 78 are 1, 2, 3, 6, 13, 26, 39, 78.
What is 78 in Roman numerals?
78 in Roman numerals is LXXVIII.
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: 15 July 2026