280
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 720
- Proper Divisor Sum (Aliquot Sum)
- 440
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 96
- Möbius Function
- 0
- Radical
- 70
- Omega Function (Ω)
- 5
- Little Omega Function (ω)
- 3
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
- yes
- Harshad Number
- yes
- Narcissistic Number
- no
- Collatz Steps
- 16
- Smith 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
- yes
- Odd
- no
Names
- German
- zweihundertachtzig· ordinal: zweihundertachtzigste
- English
- two hundred eighty· ordinal: two hundred eightieth
- Spanish
- doscientos ochenta· ordinal: 280º
- French
- deux cent quatre-vingts· ordinal: deux cent quatre-vingtsième
- Italian
- duecentoottanta· ordinal: 280º
- Latin
- ducenti octoginta· ordinal: 280.
- Portuguese
- duzentos e oitenta· ordinal: 280º
Appears in sequences
- Number of trees of diameter 4.at n=17A000094
- a(n) = floor(n^2/3).at n=29A000212
- Octagonal numbers: n*(3*n-2). Also called star numbers.at n=10A000567
- a(n) = a(n-1) + 2^a(n-2).at n=7A000643
- Euler's "numerus idoneus" (or "numeri idonei", or idoneal, or suitable, or convenient numbers).at n=51A000926
- Numbers that are divisible by at least three different primes.at n=51A000977
- Generalized octagonal numbers: k*(3*k-2), k=0, +- 1, +- 2, +-3, ...at n=19A001082
- Numbers that are the sum of 4 cubes in more than 1 way.at n=12A001245
- Triangle in which k-th number (0<=k<=n) in n-th row (0<=n) is number of dodecads in Golay code G_24 containing k given points and missing n-k given points.at n=9A001294
- Triangle in which k-th number (0<=k<=n) in n-th row (0<=n) is number of dodecads in Golay code G_24 containing k given points and missing n-k given points.at n=6A001294
- a(n) is the number of partitions of n into at most 3 parts; also partitions of n+3 in which the greatest part is 3; also number of unlabeled multigraphs with 3 nodes and n edges.at n=55A001399
- Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^8 in powers of x.at n=9A001486
- Winning moves in Fibonacci nim.at n=49A001581
- The coding-theoretic function A(n,4,3).at n=41A001839
- v-pile counts for the 4-Wythoff game with i=2.at n=53A001966
- MacMahon's solid partitions of n in which 4 is the smallest summand.at n=7A002045
- Absolute value of Glaisher's beta'(2n+1).at n=16A002291
- Numbers x such that x^2 + y^2 = p^2 = A002144(n)^2, x < y.at n=41A002366
- Let p = A007645(n) be the n-th generalized cuban prime and write p^2 = x^2 + 3*y^2 with y > 0; a(n) = y.at n=47A002368
- Expansion of a modular function for Gamma_0(15).at n=9A002510