809
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 17
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 810
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 808
- Möbius Function
- -1
- Radical
- 809
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- no
- Perfect Square
- no
- Perfect Cube
- no
- Pentagonal Number
- no
- Hexagonal Number
- no
- Lucas Number
- no
- Tetrahedral Number
- no
- Pell Number
- no
- Tribonacci Number
- no
- Pronic Number
- no
Recreational
- Happy Number
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 46
- Smith Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- yes
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 140
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Names
- German
- achthundertneun· ordinal: achthundertneunste
- English
- eight hundred nine· ordinal: eight hundred ninth
- Spanish
- ochocientos nueve· ordinal: 809º
- French
- huit cent neuf· ordinal: huit cent neufième
- Italian
- ottocentonove· ordinal: 809º
- Latin
- octingenti novem· ordinal: 809.
- Portuguese
- oitocentos e nove· ordinal: 809º
Appears in sequences
- Primes p == 3, 9, 11 (mod 20) such that 2p+1 is also prime.at n=15A000355
- Numbers beginning with letter 'e' in English.at n=22A000873
- Irregular primes: primes p such that at least one of the numerators of the Bernoulli numbers B_2, B_4, ..., B_{p-3} (A000367) is divisible by p.at n=53A000928
- Primes with 3 as smallest primitive root.at n=32A001123
- Lesser of twin primes.at n=30A001359
- Numbers in which every digit contains at least one loop (version 1).at n=35A001743
- Numbers k such that phi(k+2) = phi(k) + 2.at n=49A001838
- From rook polynomials.at n=6A001925
- Glaisher's G numbers.at n=3A002111
- The square sieve.at n=50A002960
- a(n) = n^3 + n^2 - 1.at n=8A003777
- a(n) = floor((n^2 + 6n - 3)/4).at n=53A004116
- Divisible only by primes congruent to 4 mod 5.at n=35A004618
- Divisible only by primes congruent to 4 mod 7.at n=25A004622
- Numbers divisible only by primes congruent to 1 mod 8.at n=33A004625
- Class 3- primes (for definition see A005109).at n=40A005111
- Sophie Germain primes p: 2p+1 is also prime.at n=34A005384
- Positions of remoteness 4 in Beans-Don't-Talk.at n=15A005696
- Odd numbers not of form p + 2^k (de Polignac numbers).at n=11A006285
- Primes p such that 2^p - 1 has at most 2 prime factors.at n=46A006514