16819
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 18620
- Proper Divisor Sum (Aliquot Sum)
- 1801
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 15180
- Möbius Function
- 0
- Radical
- 1529
- Omega Function (Ω)
- 3
- 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
- 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
- 66
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- Base-8 Armstrong or narcissistic numbers (written in base 10).at n=14A010354
- Numbers n such that sigma(n) and d(n) are both harmonic (Ore) numbers.at n=7A071767
- t(n)_n where t() = triangular numbers A000217.at n=42A122634
- a(n) = 841*n - 1.at n=19A158402
- a(n) = 20*n^2 - 1.at n=28A158491
- Base 8 perfect digital invariants (written in base 10): numbers equal to the sum of the k-th powers of their base-8 digits, for some k.at n=35A162231
- Integer k associated with the conjectured record-breaking length A226670(n) of primitive Collatz-like 3x+k cycles.at n=24A226671
- Integer k associated with the conjectured record-breaking number A226673(n) of odd elements in a primitive Collatz-like 3x+k cycle.at n=21A226674
- Reversal of base-n digits of largest prime < n^3.at n=27A329931
- E.g.f.: exp(-x/(1 - x)) / (1 - 2*x).at n=6A331688
- a(n) is the least number k such that A349474(k) = A349474(k+1) = n, or -1 if no such k exists.at n=11A349500
- Place n equally spaced points on each side of an equilateral triangle, and join each of these points by a chord to the 2*n new points on the other two sides: sequence gives number of regions in the resulting planar graph.at n=10A366486
- Irregular triangle read by rows: T(n,k) is the number of free polyominoes with n cells and width k, n >= 1, 1 <= k <= ceiling(n/2).at n=55A379623