209
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 11
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 240
- Proper Divisor Sum (Aliquot Sum)
- 31
- 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
- 180
- Möbius Function
- 1
- Radical
- 209
- 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
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 39
- Smith 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
Names
- German
- zweihundertneun· ordinal: zweihundertneunste
- English
- two hundred nine· ordinal: two hundred ninth
- Spanish
- doscientos nueve· ordinal: 209º
- French
- deux cent neuf· ordinal: deux cent neufième
- Italian
- duecentonove· ordinal: 209º
- Latin
- ducenti novem· ordinal: 209.
- Portuguese
- duzentos e nove· ordinal: 209º
Appears in sequences
- a(n) = n*(n+3)/2.at n=19A000096
- Number of steps to reach 1 in sequence A000546.at n=52A000547
- Number of steps to reach 1 in sequence A000546.at n=30A000547
- Expansion of Product_{k>=0} (1 + x^(2k+1)); number of partitions of n into distinct odd parts; number of self-conjugate partitions; number of symmetric Ferrers graphs with n nodes.at n=60A000700
- Number of partitions of n into relatively prime parts. Also aperiodic partitions.at n=16A000837
- Moran numbers: k such that k/(sum of digits of k) is prime.at n=20A001101
- Number of partitions of n into squares.at n=63A001156
- Triangle read by rows, in which row n consists of n(n+m) for m = 1 .. n-1.at n=52A001283
- Numbers of form m*k with m+1 <= k <= 2m-1.at n=58A001284
- a(n) = 4*a(n-1) - a(n-2) with a(0) = 0, a(1) = 1.at n=5A001353
- Number of stacks, or planar partitions of n; also weakly unimodal compositions of n.at n=10A001523
- a(n) = (10n+1)*(10n+9).at n=1A001535
- Perrin sequence (or Perrin numbers, or Ondrej Such sequence): a(n) = a(n-2) + a(n-3) with a(0) = 3, a(1) = 0, a(2) = 2.at n=19A001608
- Hit polynomials.at n=4A001889
- a(n) = floor((n+2/3)*(5+sqrt(13))/2); v-pile positions in the 3-Wythoff game.at n=48A001960
- A Beatty sequence: floor(n * (sqrt(5) + 3)).at n=39A001962
- Numbers k such that 3*2^k + 1 is prime.at n=13A002253
- Numbers k such that 11*2^k + 1 is prime.at n=10A002261
- Numbers y such that p^2 = x^2 + y^2, 0 < x < y, p = A002144(n).at n=23A002365
- Numbers m such that m^2 + m + 1 is prime.at n=59A002384