820
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
- 12
- Divisor Sum
- 1764
- Proper Divisor Sum (Aliquot Sum)
- 944
- 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
- 320
- Möbius Function
- 0
- Radical
- 410
- Omega Function (Ω)
- 4
- 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
- yes
- 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
- 28
- 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
- achthundertzwanzig· ordinal: achthundertzwanzigste
- English
- eight hundred twenty· ordinal: eight hundred twentieth
- Spanish
- ochocientos veinte· ordinal: 820º
- French
- huit cent vingt· ordinal: huit cent vingtième
- Italian
- ottocentoventi· ordinal: 820º
- Latin
- octingenti viginti· ordinal: 820.
- Portuguese
- oitocentos e vinte· ordinal: 820º
Appears in sequences
- Central factorial numbers: A008955(n,3).at n=1A000597
- Numbers beginning with letter 'e' in English.at n=33A000873
- Number of n X n symmetric matrices with (0,1) entries and all row sums 2.at n=6A000986
- a(n) = sigma_2(n): sum of squares of divisors of n.at n=26A001157
- Central factorial numbers: second right-hand column of triangle A008955.at n=4A001819
- Related to Zarankiewicz's problem.at n=38A001841
- Numbers k such that 25*4^k + 1 is prime.at n=20A002263
- a(n) = (9^n - 1)/8.at n=4A002452
- Number of partitions of n into parts 1/2, 3/4, 7/8, 15/16, etc.at n=12A002843
- Number of cyclic Steiner triple systems of order 2n+1.at n=18A002885
- Number of partitions of n into parts 5k+2 or 5k+3.at n=52A003106
- Number of coprime chains with largest member n.at n=60A003139
- Number of coprime chains with largest member prime(n).at n=17A003140
- a(n+1) = 1 + a( floor(n/1) ) + a( floor(n/2) ) + ... + a( floor(n/n) ).at n=20A003318
- Numbers that are a sum of distinct positive cubes in more than one way.at n=18A003998
- Number of walks of length 2n+8 in the path graph P_9 from one end to the other.at n=3A005024
- Coefficients of period polynomials.at n=11A006308
- Coloring a circuit with 4 colors.at n=7A006342
- Numbers whose sum of divisors is a square.at n=37A006532
- From a partition of the integers.at n=19A006628