15
domain: N
Properties
Digital Properties
- Digit Count
- 2
- 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
- 24
- Proper Divisor Sum (Aliquot Sum)
- 9
- 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
- 8
- Möbius Function
- 1
- Radical
- 15
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- yes
- 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
- 17
- Smith Number
- no
Classification
- Natural
- yes
- Even
- no
- Odd
- yes
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
- yes
- Carmichael Number
- no
Names
- German
- fünfzehn· ordinal: fünfzehnte
- English
- fifteen· ordinal: fifteenth
- Spanish
- quince· ordinal: decimoquinto
- French
- quinze· ordinal: quinzième
- Italian
- quindici· ordinal: 15º
- Latin
- quindecim· ordinal: 15.
- Portuguese
- quinze· ordinal: 15º
Appears in sequences
- Number of groups of order n.at n=24A000001
- Number of groups of order n.at n=54A000001
- Number of groups of order n.at n=81A000001
- Number of groups of order n.at n=84A000001
- Integer part of square root of n-th prime.at n=48A000006
- Integer part of square root of n-th prime.at n=49A000006
- Integer part of square root of n-th prime.at n=50A000006
- Integer part of square root of n-th prime.at n=51A000006
- Integer part of square root of n-th prime.at n=52A000006
- Integer part of square root of n-th prime.at n=53A000006
- Number of ways of making change for n cents using coins of 1, 2, 5, 10 cents.at n=12A000008
- Expansion of Product_{m >= 1} (1 + x^m); number of partitions of n into distinct parts; number of partitions of n into odd parts.at n=12A000009
- Number of primitive permutation groups of degree n.at n=26A000019
- Mosaic numbers or multiplicative projection of n: if n = Product (p_j^k_j) then a(n) = Product (p_j * k_j).at n=14A000026
- The positive integers. Also called the natural numbers, the whole numbers or the counting numbers, but these terms are ambiguous.at n=14A000027
- Numbers that are not squares (or, the nonsquares).at n=11A000037
- a(n) is the number of partitions of n (the partition numbers).at n=7A000041
- Number of integers <= 2^n of form x^2 - 2y^2.at n=5A000047
- 1-digit numbers arranged in alphabetical order, then the 2-digit numbers arranged in alphabetical order, then the 3-digit numbers, etc.at n=22A000052
- A Beatty sequence: a(n) = floor(n/(e-2)).at n=10A000062