19
19 is a prime number, the atomic number of potassium, and forms a twin-prime pair with 17.
- Odd
- Prime
Where 19 fits
Why 19 is special
19's mathematics (prime, twin with 17) is ordinary by design — its best-known everyday reference is jokingly practical: 'the 19th hole' golfing idiom for the clubhouse bar.
Same number, different meanings
How 19 is understood across different contexts — never implying one meaning because of another.
- Mathematics
19's mathematics (prime, twin with 17) is ordinary by design — its best-known everyday reference is jokingly practical: 'the 19th hole' golfing idiom for the clubhouse bar.
- Science
19 is the atomic number of potassium, an essential electrolyte.
- Sport
'The 19th hole' is a well-known golfing idiom for the clubhouse bar, humorously extending a standard 18-hole round by one more notional 'hole'.
19 is part of
Factors & digit properties
- Divisors (2)
- 1, 19
- Prime factorisation
- 19
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 19
- Binary
- 10011
- Octal
- 23
- Hexadecimal
- 13
- Roman numeral
- XIX
- Scientific notation
- 1.900 × 10^1
Other mathematical patterns
- Deficient number
- Happy number
- Twin prime
Related numbers & connections
19 is a factor of 38 (19 × 2 = 38).
View 38 →18 (a standard golf round) and 19 (the 'clubhouse' 19th hole) are consecutive integers connected by the same golfing idiom.
View 18 →17 and 19 are twin primes — two primes exactly two apart.
View 17 →Science
19 is the atomic number of potassium, an essential electrolyte.
DocumentedScience
Sport
'The 19th hole' is a well-known golfing idiom for the clubhouse bar, humorously extending a standard 18-hole round by one more notional 'hole'.
Widely documentedSport
Common questions
Is 19 a prime number?
Yes, 19 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 19?
The factors of 19 are 1, 19.
What is 19 in Roman numerals?
19 in Roman numerals is XIX.
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