23
domain: N
Properties
Digital Properties
- Digit Count
- 2
- Digit Sum
- 5
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 24
- Proper Divisor Sum (Aliquot Sum)
- 1
- 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
- 22
- Möbius Function
- -1
- Radical
- 23
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- no
- Narcissistic Number
- no
- Collatz Steps
- 15
- Smith Number
- no
Classification
- Natural
- yes
- Even
- no
- Odd
- yes
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- yes
- Safe Prime
- yes
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 9
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Names
- German
- dreiundzwanzig· ordinal: dreiundzwanzigste
- English
- twenty-three· ordinal: twenty-third
- Spanish
- veintitrés· ordinal: 23º
- French
- vingt-trois· ordinal: vingt-troisième
- Italian
- ventitre· ordinal: 23º
- Latin
- viginti tres· ordinal: 23.
- Portuguese
- vinte e três· ordinal: 23º
Appears in sequences
- Number of n-bead necklaces (turning over is allowed) where complements are equivalent.at n=9A000011
- Smallest prime power >= n.at n=19A000015
- Smallest prime power >= n.at n=20A000015
- Smallest prime power >= n.at n=21A000015
- Smallest prime power >= n.at n=22A000015
- Mosaic numbers or multiplicative projection of n: if n = Product (p_j^k_j) then a(n) = Product (p_j * k_j).at n=22A000026
- The positive integers. Also called the natural numbers, the whole numbers or the counting numbers, but these terms are ambiguous.at n=22A000027
- Let k = p_1^e_1 p_2^e_2 p_3^e_3 ... be the prime factorization of n. Sequence gives k such that the sum of the numbers of 1's in the binary expansions of e_1, e_2, e_3, ... is odd.at n=11A000028
- Let A(n) = #{(i,j): i^2 + j^2 <= n}, V(n) = Pi*n, P(n) = A(n) - V(n); A000099 gives values of n where |P(n)| sets a new record; sequence gives closest integer to P(A000099(n)).at n=20A000036
- Numbers that are not squares (or, the nonsquares).at n=18A000037
- Local stops on New York City 1 Train (Broadway-7 Avenue Local) subway.at n=2A000053
- Local stops on New York City A line subway.at n=2A000054
- Number of trees with n unlabeled nodes.at n=8A000055
- Primes that divide at least one term in every Fibonacci sequence.at n=3A000057
- Numbers k such that (2k)^4 + 1 is prime.at n=8A000059
- A Beatty sequence: a(n) = floor(n/(e-2)).at n=16A000062
- Number of positive integers <= 2^n of form 2*x^2 + 3*y^2.at n=6A000075
- Number of mixed Husimi trees with n nodes; or polygonal cacti with bridges.at n=6A000083
- a(n) is the number of compositions of n in which the maximal part is 3.at n=7A000100
- a(n) is the least number m such that the n-th prime is the least quadratic nonresidue modulo m.at n=2A000229