15519
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 23680
- Proper Divisor Sum (Aliquot Sum)
- 8161
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8856
- Möbius Function
- -1
- Radical
- 15519
- 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
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 120
- Smith Number
- no
- Vampire 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
Appears in sequences
- Numbers n such that 39*2^n-1 is a prime.at n=13A050545
- Prime(n)*prime(2*n)+prime(n)+prime(2*n).at n=21A072672
- Interprimes (A024675) which are of the form s*prime, s=21.at n=32A075296
- a(n) = Sum_{k=0..floor(n/6)} binomial(n-3k,3k).at n=23A100134
- Number of positive integers <= 10^n that are divisible by no prime exceeding 13.at n=8A106629
- G.f.: 1/(1 - x^2/(1 - x^5/(1 - x^8/(1 - x^11/(1 - x^14/(1 - x^17/(1 -...- x^(3*n-1)/(1 -...)))))))), a continued fraction.at n=49A206738
- Number of ways of writing n as the sum of 7 triangular numbers.at n=40A226252
- Number of partitions p of n such that (number of numbers of the form 5k + 4 in p) is a part of p.at n=39A241553
- p-INVERT of the positive integers, where p(S) = 1 - S^3.at n=11A290891
- p-INVERT of (0,1,0,1,0,1,...), where p(S) = 1 - S^3.at n=23A291217
- Composite numbers k coprime to 13 such that k divides A006190(k) - Kronecker(13,k).at n=22A327654
- a(n) is the number of edges formed by n-secting the angles of a heptagon.at n=27A335759
- Expansion of Product_{k>=1} 1 / (1 + 2^(k-1)*x^k).at n=16A352402
- Expansion of (1 + x)^2/(1 - x^3*(1 + x)^3).at n=21A375321