15021
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 9
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 21710
- Proper Divisor Sum (Aliquot Sum)
- 6689
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10008
- Möbius Function
- 0
- Radical
- 5007
- Omega Function (Ω)
- 3
- 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
- yes
- Harshad Number
- yes
- Narcissistic Number
- no
- Collatz Steps
- 63
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- Max_{k=0..n} { Number of partitions of n into exactly k parts }.at n=49A002569
- Molien series for A_11.at n=38A008634
- Number of partitions of n into at most 11 parts.at n=38A008640
- a(n) = T(n,n) + T(n,m+1) + ... + T(n,n), where m=[ (n+2)/2 ], T given by A027011.at n=12A027021
- Numbers k such that k^2 is palindromic in base 8.at n=44A029805
- a(n) = smallest positive integer that cannot be obtained using the number n at most n times and the operations +, -, *, /, where intermediate subexpressions must be integers.at n=14A071848
- Smaller terms in the pairs of numbers (a < b) in the sequence {a,b}-> {Max[{a,b}]-Min[{a,b}],k*Min[{a,b}]} with k=3 and the first pair {a=1,b=2}. See A075256.at n=41A075257
- Numbers such that the digital sum base 2 and the digital sum base 3 and the digital sum base 10 all are equal.at n=18A135120
- a(0)=a(1)=1. For n >= 2, if a(n-1) is coprime to n, then a(n) = a(n-1) + a(n-2). Otherwise, a(n)=1.at n=49A139047
- Square array T(n, k) = Product_{j=1..n} ( Sum_{i=0..j-1} ( (k+1)^7 - Sum_{m=1..5} (k+1)^m )^i ) with T(n, 0) = n!, read by antidiagonals.at n=17A156888
- a(n) = n^2 + 731*n + 1.at n=20A180919
- Number of lower triangular n X n arrays colored with integers 0 upwards introduced in row major order, with no element equal to any diagonal or antidiagonal neighbor, and containing the value n(n+1)/2-3.at n=5A211959
- T(n,k)=Number of lower triangular n X n arrays colored with integers 0 upwards introduced in row major order, with no element equal to any diagonal or antidiagonal neighbor, and containing the value n(n+1)/2-k-1.at n=26A211963
- Total sum of parts of multiplicity 9 in all partitions of n.at n=41A222737
- Number of partitions p of n such that the number of numbers having multiplicity 1 in p is a part or the number of numbers having multiplicity > 1 is a part.at n=36A239737
- Numbers that are equal to the sum of the number of divisors of their k first powers, for some k.at n=17A270389
- Binomial(n,4) - A290447(n).at n=37A290461