1823
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 14
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 1824
- 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
- 1822
- Möbius Function
- -1
- Radical
- 1823
- 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
- 161
- 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
- no
- Safe Prime
- yes
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 281
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p == 7, 19, 23 (mod 40) such that (p-1)/2 is also prime.at n=16A000353
- Primes with 5 as smallest primitive root.at n=38A001124
- Safe primes p: (p-1)/2 is also prime.at n=35A005385
- Primes of form n^2 + n + 17.at n=32A007635
- Primes of form 3*k^2 - 3*k + 23.at n=22A007637
- Coordination sequence T2 for Zeolite Code MEI.at n=31A008147
- Coordination sequence T4 for Zeolite Code MFI.at n=27A008167
- Expansion of 1/( Product_{j=0..5} (1-x^(2*j+1)) ).at n=57A008675
- Number of distinct orders of permutations of n objects; number of nonisomorphic cyclic subgroups of symmetric group S_n.at n=58A009490
- Numbers n such that phi(n + 9) | sigma(n) for n not congruent to 0 (mod 3).at n=32A015849
- "Pascal sweep" for k=5: draw a horizontal line through the 1 at C(k,0) in Pascal's triangle; rotate this line and record the sum of the numbers on it (excluding the initial 1).at n=69A019306
- Numbers k such that the continued fraction for sqrt(k) has period 28.at n=32A020367
- Primes that remain prime through 2 iterations of function f(x) = 3x + 10.at n=46A023249
- Primes that remain prime through 2 iterations of function f(x) = 9x + 4.at n=30A023266
- Primes that remain prime through 2 iterations of function f(x) = 10x + 3.at n=37A023269
- Discriminants of quartic fields with 2 complex conjugates (negated).at n=40A023681
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = A023532, t = (primes).at n=39A024377
- Duplicate of A024377.at n=39A025069
- s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = A023532, t = (primes).at n=38A025077
- a(n) = sum of the numbers between the two n's in A026358.at n=21A026361