77
77 is the atomic number of iridium — an unusually iridium-rich rock layer worldwide provides key evidence for the asteroid impact linked to the dinosaurs' extinction.
- Odd
- Composite
Where 77 fits
Why 77 is special
77's element connects a rare metal to one of the most consequential events in Earth's history, dated to about 66 million years ago.
Same number, different meanings
How 77 is understood across different contexts — never implying one meaning because of another.
- Mathematics
77's element connects a rare metal to one of the most consequential events in Earth's history, dated to about 66 million years ago.
- Science
77 is the atomic number of iridium.
- History
A thin, unusually iridium-rich layer found in rock worldwide, dating to about 66 million years ago, is central evidence for the asteroid-impact explanation of the mass extinction that ended the age of dinosaurs.
77 is part of
Factors & digit properties
- Divisors (4)
- 1, 7, 11, 77
- Prime factorisation
- 7 × 11
- Digit sum
- 14
- Digital root
- 5
Representations
- Decimal
- 77
- Binary
- 1001101
- Octal
- 115
- Hexadecimal
- 4d
- Roman numeral
- LXXVII
- Scientific notation
- 7.700 × 10^1
Other mathematical patterns
- Palindromic number
- Deficient number
- Repdigit
- Semiprime
Related numbers & connections
11 is a factor of 77 (11 × 7 = 77).
View 11 →Mathematically related
- has factor11
why?
Strength 0.50, confidence "high".
Science
77 is the atomic number of iridium.
DocumentedScience
History
A thin, unusually iridium-rich layer found in rock worldwide, dating to about 66 million years ago, is central evidence for the asteroid-impact explanation of the mass extinction that ended the age of dinosaurs.
DocumentedHistory
Common questions
Is 77 a prime number?
No, 77 is not prime.
What are the factors of 77?
The factors of 77 are 1, 7, 11, 77.
What is 77 in Roman numerals?
77 in Roman numerals is LXXVII.
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