13
domain: N
Properties
Digital Properties
- Digit Count
- 2
- Digit Sum
- 4
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 14
- 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
- 12
- Möbius Function
- -1
- Radical
- 13
- 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
- yes
- 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
- yes
- Pronic Number
- no
Recreational
- Happy Number
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 9
- 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
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 6
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Names
- German
- dreizehn· ordinal: dreizehnte
- English
- thirteen· ordinal: thirteenth
- Spanish
- trece· ordinal: decimotercero
- French
- treize· ordinal: treizième
- Italian
- tredici· ordinal: 13º
- Latin
- tredecim· ordinal: 13.
- Portuguese
- treze· ordinal: 13º
Appears in sequences
- Number of groups of order n.at n=56A000001
- Number of groups of order n.at n=60A000001
- Integer part of square root of n-th prime.at n=39A000006
- Integer part of square root of n-th prime.at n=40A000006
- Integer part of square root of n-th prime.at n=41A000006
- Integer part of square root of n-th prime.at n=42A000006
- Integer part of square root of n-th prime.at n=43A000006
- Smallest prime power >= n.at n=11A000015
- Smallest prime power >= n.at n=12A000015
- Number of positive integers <= 2^n of form x^2 + 16*y^2.at n=6A000018
- Number of primitive permutation groups of degree n.at n=64A000019
- Coefficients of the 3rd-order mock theta function f(q).at n=13A000025
- Mosaic numbers or multiplicative projection of n: if n = Product (p_j^k_j) then a(n) = Product (p_j * k_j).at n=12A000026
- The positive integers. Also called the natural numbers, the whole numbers or the counting numbers, but these terms are ambiguous.at n=12A000027
- 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=7A000028
- Number of necklaces with n beads of 2 colors, allowing turning over (these are also called bracelets).at n=6A000029
- 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=9A000036
- 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=10A000036
- 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=11A000036
- Numbers that are not squares (or, the nonsquares).at n=9A000037