321
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 6
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 432
- Proper Divisor Sum (Aliquot Sum)
- 111
- 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
- 212
- Möbius Function
- 1
- Radical
- 321
- 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
- no
- Narcissistic Number
- no
- Collatz Steps
- 24
- 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
- dreihunderteinundzwanzig· ordinal: dreihunderteinundzwanzigste
- English
- three hundred twenty-one· ordinal: three hundred twenty-first
- Spanish
- trescientos veintiuno· ordinal: 321º
- French
- trois cent vingt et un· ordinal: trois cent vingt et unième
- Italian
- trecentoventuno· ordinal: 321º
- Latin
- trecenti viginti unus· ordinal: 321.
- Portuguese
- trezentos e vinte e um· ordinal: 321º
Appears in sequences
- a(n) = a(n-1) + a(n-2)^2 for n >= 2 with a(0) = 0 and a(1) = 1.at n=8A000278
- a(n) = (n-1)*2^n + 1.at n=6A000337
- Hexanacci numbers with a(0) = ... = a(5) = 1.at n=12A000383
- Concatenation of numbers from n down to 1.at n=2A000422
- Moser-de Bruijn sequence: sums of distinct powers of 4.at n=25A000695
- Number of permutations of length n by rises.at n=4A001277
- Number of partitions of n into at most 4 parts.at n=31A001400
- Triangle of values of 2-d recurrence.at n=47A001404
- a(n) = a(n-1) + a(n-2) + 1, with a(0) = 0 and a(1) = 2.at n=11A001610
- Squares written in base 6.at n=11A001741
- a(n) = 3 * prime(n).at n=27A001748
- Centered 4-dimensional orthoplex numbers (crystal ball sequence for 4-dimensional cubic lattice).at n=4A001846
- Central Delannoy numbers: a(n) = Sum_{k=0..n} C(n,k)*C(n+k,k).at n=4A001850
- a(n) = 5*a(n-1) - a(n-2).at n=4A002320
- Numbers k such that binomial(2*k,k) is divisible by (k+1)^2.at n=29A002503
- Numbers k such that (k^2 + k + 1)/13 is prime.at n=17A002642
- Numbers k such that (k^2 + 1)/2 is prime.at n=50A002731
- a(0) = 1; for n > 0, a(n) = a(n-1) + floor(sqrt(a(n-1))).at n=38A002984
- a(n+1) = a(n) + 2n*(2n+1)*a(n-1), with a(0) = a(1) = 1.at n=4A003148
- Number of unrooted achiral trees with n nodes.at n=16A003244