231
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
- 8
- Divisor Sum
- 384
- Proper Divisor Sum (Aliquot Sum)
- 153
- 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
- 120
- Möbius Function
- -1
- Radical
- 231
- Omega Function (Ω)
- 3
- 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
- yes
- 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
- 127
- Smith Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- zweihunderteinunddreißig· ordinal: zweihunderteinunddreißigste
- English
- two hundred thirty-one· ordinal: two hundred thirty-first
- Spanish
- doscientos treinta y uno· ordinal: 231º
- French
- deux cent trente et un· ordinal: deux cent trente et unième
- Italian
- duecentotrentuno· ordinal: 231º
- Latin
- ducenti triginta unus· ordinal: 231.
- Portuguese
- duzentos e trinta e um· ordinal: 231º
Appears in sequences
- a(n) is the number of partitions of n (the partition numbers).at n=16A000041
- Local stops on New York City 1 Train (Broadway-7 Avenue Local) subway.at n=26A000053
- Denumerants: Expansion of 1/((1-x)*(1-x^2)*(1-x^5)).at n=64A000115
- Triangle of numbers related to triangle A049213; generalization of Stirling numbers of second kind A008277, Bessel triangle A001497.at n=6A000369
- Topswops (2): start by shuffling n cards labeled 1..n. If the top card is m, reverse the order of the top m cards. Repeat until 1 gets to the top, then stop. Suppose the whole deck is now sorted (if not, discard this case). a(n) is the maximal number of steps before 1 got to the top.at n=19A000376
- Hexagonal numbers: a(n) = n*(2*n-1).at n=11A000384
- Number of compositions of n into 3 ordered relatively prime parts.at n=22A000741
- Lucky numbers.at n=44A000959
- Numbers that are divisible by at least three different primes.at n=37A000977
- a(n) = a(n-1)^2 - a(n-2)^2.at n=5A001042
- Dimensions (sorted, with duplicates removed) of real simple Lie algebras.at n=50A001066
- Number of degree-n permutations of order exactly 2.at n=6A001189
- Triangle read by rows, in which row n consists of n(n+m) for m = 1 .. n-1.at n=54A001283
- Numbers of form m*k with m+1 <= k <= 2m-1.at n=65A001284
- Concatenations of cyclic permutations of initial positive integers.at n=4A001292
- Triangle of values of 2-d recurrence.at n=36A001404
- Nearest integer to 2*n*log(n).at n=33A001618
- Sorting numbers: number of comparisons for merge insertion sort of n elements.at n=51A001768
- Numerators in expansion of 1/sqrt(1-x).at n=6A001790
- Centered octahedral numbers (crystal ball sequence for cubic lattice).at n=5A001845