26
domain: N
Properties
Digital Properties
- Digit Count
- 2
- Digit Sum
- 8
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 42
- Proper Divisor Sum (Aliquot Sum)
- 16
- 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
- 12
- Möbius Function
- 1
- Radical
- 26
- 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
- 10
- Smith Number
- no
Classification
- Natural
- yes
- Even
- yes
- Odd
- 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
Names
- German
- sechsundzwanzig· ordinal: sechsundzwanzigste
- English
- twenty-six· ordinal: twenty-sixth
- Spanish
- veintiséis· ordinal: 26º
- French
- vingt-six· ordinal: vingt-sixième
- Italian
- ventisei· ordinal: 26º
- Latin
- viginti sex· ordinal: 26.
- Portuguese
- vinte e seis· ordinal: 26º
Appears in sequences
- Number of series-reduced trees with n nodes.at n=12A000014
- Mosaic numbers or multiplicative projection of n: if n = Product (p_j^k_j) then a(n) = Product (p_j * k_j).at n=25A000026
- The positive integers. Also called the natural numbers, the whole numbers or the counting numbers, but these terms are ambiguous.at n=25A000027
- Numbers that are not squares (or, the nonsquares).at n=20A000037
- Number of integers <= 2^n of form x^2 - 2y^2.at n=6A000047
- A Beatty sequence: a(n) = floor(n/(e-2)).at n=18A000062
- Odious numbers: numbers with an odd number of 1's in their binary expansion.at n=13A000069
- Number of self-inverse permutations on n letters, also known as involutions; number of standard Young tableaux with n cells.at n=5A000085
- Let A(n) = #{(i,j): i^2 + j^2 <= n}, V(n) = Pi*n, P(n) = A(n) - V(n); sequence gives values of n where |P(n)| sets a new record.at n=6A000099
- Denumerants: Expansion of 1/((1-x)*(1-x^2)*(1-x^5)).at n=19A000115
- Number of binary partitions: number of partitions of 2n into powers of 2.at n=7A000123
- Cake numbers: maximal number of pieces resulting from n planar cuts through a cube (or cake): C(n+1,3) + n + 1.at n=5A000125
- Number of oriented rooted trees with n nodes. Also rooted trees with n nodes and 2-colored non-root nodes.at n=3A000151
- Number of mixed Husimi trees with n nodes; or rooted polygonal cacti with bridges.at n=5A000237
- Number of trees with n nodes, 2 of which are labeled.at n=3A000243
- a(n) = number of solid (i.e., three-dimensional) partitions of n.at n=4A000293
- Expansion of g.f. Product_{k >= 1} (1 - x^k)^(-k*(k+1)/2).at n=4A000294
- Eulerian numbers (Euler's triangle: column k=2 of A008292, column k=1 of A173018).at n=5A000295
- Coefficients of iterated exponentials.at n=2A000310
- Schroeder's fourth problem; also series-reduced rooted trees with n labeled leaves; also number of total partitions of n.at n=4A000311