15421
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 17632
- Proper Divisor Sum (Aliquot Sum)
- 2211
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 13212
- Möbius Function
- 1
- Radical
- 15421
- 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
- 53
- Smith Number
- no
- Vampire Number
- 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
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- a(n) = n*(5*n^2 - 2)/3.at n=21A004466
- Crystal ball sequence for A_4 lattice.at n=8A008384
- Expansion of 1/((1-3x)*(1-4x)*(1-5x)*(1-6x)).at n=4A028025
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 92 ones.at n=5A031860
- Denominators of continued fraction convergents to sqrt(546).at n=10A042045
- a(n) = ceiling(2^(n+1)/n).at n=16A053639
- Surround numbers of a length 2n zig-zag.at n=35A060641
- Generalized Catalan numbers C(-6; n).at n=5A064328
- Partial sums of usigma(n)^2: square of the sum of unitary divisors of n.at n=28A074789
- Triangle read by rows: T(n,k) = number of forests of k labeled rooted trees of height at most 1, with n labels, where any root may contain >= 1 labels, n >= 0, 0 <= k <= n.at n=31A143395
- Triangle read by rows: 3-Stirling numbers of the second kind.at n=31A143495
- Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 1100-0100-0111 pattern in any orientation.at n=15A146441
- Row sums of A163357 and A163359 divided by 4.at n=41A163477
- Triangle read by rows: T(n,k) (1 <= k <= n) = Steffensen's bracket function [n,n-k].at n=32A241168
- Steffensen's bracket function [n,3].at n=7A241169
- The broken eggs problem.at n=36A256101
- Number of n X 6 0..1 arrays with every element unequal to 0, 1, 3, 5 or 6 king-move adjacent elements, with upper left element zero.at n=6A304667
- Number of nX7 0..1 arrays with every element unequal to 0, 1, 3, 5 or 6 king-move adjacent elements, with upper left element zero.at n=5A304668
- Number of separable partitions of n in which the number of distinct (repeatable) parts is 4.at n=47A325648
- a(n) = A108625(n,2*n).at n=4A363867