87
87 is the atomic number of francium, among the most unstable elements found in nature.
- Odd
- Composite
Where 87 fits
Why 87 is special
87's element barely exists: francium's longest-lived isotope has a half-life of only about 22 minutes.
Factors & digit properties
- Divisors (4)
- 1, 3, 29, 87
- Prime factorisation
- 3 × 29
- Digit sum
- 15
- Digital root
- 6
Representations
- Decimal
- 87
- Binary
- 1010111
- Octal
- 127
- Hexadecimal
- 57
- Roman numeral
- LXXXVII
- Scientific notation
- 8.700 × 10^1
Other mathematical patterns
- Deficient number
- Semiprime
- Lucky number (mathematical sieve)
Related numbers & connections
29 is a factor of 87 (29 × 3 = 87).
View 29 →Mathematically related
- has factor29
why?
Strength 0.50, confidence "high".
Science
87 is the atomic number of francium, among the most unstable naturally occurring elements, with a longest-lived isotope's half-life of only about 22 minutes.
DocumentedScience
Mathematics
87 factors as 3 × 29.
DocumentedMathematics
Common questions
Is 87 a prime number?
No, 87 is not prime.
What are the factors of 87?
The factors of 87 are 1, 3, 29, 87.
What is 87 in Roman numerals?
87 in Roman numerals is LXXXVII.
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