1999
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 28
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 2000
- 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
- 1998
- Möbius Function
- -1
- Radical
- 1999
- 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
- 50
- 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
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 303
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p of the form 3k+1 such that sum_{x=1..p} cos(2*Pi*x^3/p) < -sqrt(p).at n=28A000923
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/6.at n=12A001136
- Centered triangular numbers: a(n) = 3*n*(n-1)/2 + 1.at n=36A005448
- Number of Twopins positions.at n=18A005689
- Expansion of (1 + 2*x^2 + x^3)/((1 - x)^2*(1 - x^3)).at n=54A008822
- Numbers in which every prefix (in base 10) is 1 or a prime.at n=53A012883
- Primes of the form x^2 + 27y^2.at n=45A014752
- Numbers n such that phi(n + 9) | sigma(n) for n not congruent to 0 (mod 3).at n=34A015849
- Seven iterations of Reverse and Add are needed to reach a palindrome.at n=29A015986
- Numbers k=3*m+1 such that 2^m == 1 (mod k).at n=47A016108
- Numbers k such that the continued fraction for sqrt(k) has period 84.at n=1A020423
- Primes that contain digits 1 and 9 only.at n=7A020457
- n-th prime p(k) such that p(k) + p(k+6) = p(k+2) + p(k+4).at n=33A022891
- Primes that remain prime through 2 iterations of the function f(x) = 2x + 5.at n=29A023243
- Primes that remain prime through 2 iterations of function f(x) = 10x + 3.at n=40A023269
- (d(n)-r(n))/5, where d = A026066 and r is the periodic sequence with fundamental period (0,3,1,0,1).at n=27A026068
- a(n) = Sum_{k=1..n-2} T(n,k) * T(n,k+2), with T given by A026703.at n=4A027254
- Number of distinct products ijk with 0 <= i < j < k <= n.at n=32A027429
- Primes that are palindromic in base 6.at n=16A029974
- Primes p such that digits of p appear in p^2.at n=38A030079