1891
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 1984
- Proper Divisor Sum (Aliquot Sum)
- 93
- 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
- 1800
- Möbius Function
- 1
- Radical
- 1891
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- yes
- Perfect Square
- no
- Perfect Cube
- no
- Pentagonal Number
- no
- Hexagonal Number
- yes
- 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
- 37
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- Squarefree Number
- yes
- Prime Power
- no
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Hexagonal numbers: a(n) = n*(2*n-1).at n=31A000384
- Centered triangular numbers: a(n) = 3*n*(n-1)/2 + 1.at n=35A005448
- Centered pentagonal numbers: (5n^2+5n+2)/2; crystal ball sequence for 3.3.3.4.4. planar net.at n=27A005891
- Pseudoprimes to base 3.at n=9A005935
- Pseudoprimes to base 5.at n=7A005936
- Independence number of de Bruijn graph of order n on two symbols.at n=11A006946
- Numbers k for which 10k+1, 10k+3, 10k+7 and 10k+9 are primes.at n=16A007811
- Coordination sequence T4 for Zeolite Code iRON.at n=31A009884
- Odd triangular numbers.at n=30A014493
- Tetranacci numbers arising in connection with current algebras sp(2)_n.at n=10A014610
- a(n) = (2*n+1)*(4*n+1).at n=15A014634
- a(n) is the sum over all floor(k^3/n), k=0 to n inclusive.at n=18A014818
- Binomial coefficients C(n,60).at n=2A017724
- Binomial coefficients C(62,n).at n=2A017778
- Fermat pseudoprimes to base 4.at n=16A020136
- Pseudoprimes to base 9.at n=23A020138
- Pseudoprimes to base 12.at n=15A020140
- Pseudoprimes to base 13.at n=14A020141
- Pseudoprimes to base 14.at n=13A020142
- Pseudoprimes to base 15.at n=8A020143