1811
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 11
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 1812
- 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
- 1810
- Möbius Function
- -1
- Radical
- 1811
- 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
- 68
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- yes
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 280
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p == 3, 9, 11 (mod 20) such that 2p+1 is also prime.at n=27A000355
- Number of binary necklaces of length n with no subsequence 00, excluding the necklace "0".at n=21A000358
- Primes with 6 as smallest primitive root.at n=18A001125
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/5.at n=4A001135
- Smallest prime p==3 (mod 8) such that Q(sqrt(-p)) has class number 2n+1.at n=11A002148
- Lucasian primes: p == 3 (mod 4) with 2*p+1 prime.at n=29A002515
- Expansion of g.f.: (1+x^3)*(1+x^4)/((1-x)*(1-x^2)^2*(1-x^4)).at n=34A004657
- Class 4+ primes (for definition see A005105).at n=30A005108
- a(n) = 1 + n/2 + 9*n^2/2.at n=20A006137
- Number of n-step spirals on hexagonal lattice.at n=14A006777
- Where the prime race among 7k+1, ..., 7k+6 changes leader.at n=16A007354
- Reflectable emirps.at n=10A007628
- Numbers n such that n, 2n+1, and 4n+3 all prime.at n=16A007700
- Least m such that if a/b < c/d are Farey fractions of order n then there exists k such that a/b < k/m < c/d, k/m reduced.at n=48A009571
- Coordination sequence T3 for Zeolite Code RUT.at n=28A009899
- Primes that contain digits 1 and 8 only.at n=5A020456
- Describe previous term from the right (method A - initial term is 8).at n=2A022512
- Numbers k such that k and 8*k + 1 are both prime.at n=49A023228
- Primes that remain prime through 2 iterations of function f(x) = 3x + 10.at n=45A023249
- Primes that remain prime through 2 iterations of function f(x) = 4x + 9.at n=37A023251