15856
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 10
- Divisor Sum
- 30752
- Proper Divisor Sum (Aliquot Sum)
- 14896
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7920
- Möbius Function
- 0
- Radical
- 1982
- Omega Function (Ω)
- 5
- 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
- 102
- 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
- yes
- Odd
- no
Appears in sequences
- Number of Twopins positions.at n=49A005686
- a(n) = n*(31*n-1)/2.at n=32A022288
- a(1) = 7; a(n+1) = a(n)-th nonprime, where nonprimes begin at 0.at n=37A025002
- Number of partitions of n into parts not of the form 17k, 17k+8 or 17k-8. Also number of partitions with at most 7 parts of size 1 and differences between parts at distance 7 are greater than 1.at n=38A035969
- Denominators of continued fraction convergents to sqrt(436).at n=10A041831
- Numbers k such that numerator of Bernoulli(2k) is divisible by the square of 59, the second irregular prime.at n=22A093058
- Expansion of (1+x)^4/(1-11*x+11*x^2-x^3).at n=4A095685
- Row sums of triangular matrix A105540, in which column n equals A105540^(n+1) when flattened as read by rows.at n=19A105541
- E.g.f.: exp(x+5/2*x^2).at n=7A115331
- Triangle read by rows: T(n,k) is the number of deco polyominoes of height n and having k 1-cell columns starting at level 0 (0<=k<=n). A deco polyomino is a directed column-convex polyomino in which the height, measured along the diagonal, is attained only in the last column.at n=49A121585
- Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, 0, 1), (0, -1, 1), (0, 1, 0), (1, 1, -1), (1, 1, 1)}.at n=7A150886
- Triangle read by rows: T(n,k) = 3*T(n-1,k-1) + 3*T(n-1,k) - 2*T(n-2,k-1) with T(n,0) = T(n,n) = 1.at n=38A152613
- Triangle read by rows: T(n,k) = 3*T(n-1,k-1) + 3*T(n-1,k) - 2*T(n-2,k-1) with T(n,0) = T(n,n) = 1.at n=42A152613
- a(n) = 512*n - 16.at n=30A157447
- a(n) = the smallest positive integer not yet occurring such that the number of divisors of 1+sum{k=1 to n} a(k) is exactly n.at n=24A177268
- a(0)=0, a(1)=1, a(n) = min{3 a(k) + (3^(n-k)-1)/2, k=0..(n-1)} for n>=2.at n=32A259653
- Positive integers congruent to 0 or 1 modulo 4 that cannot be written as x^3 + y^2 + z^2 with x,y,z nonnegative integers.at n=13A275083
- Number of compositions (ordered partitions) of n into parts with an odd number of prime divisors (counted with multiplicity).at n=27A286226
- Strings of 5 digits from 1...9, such that no formula using the single digits in the given order exists that evaluates to 0.at n=36A288355
- Coefficients of 1/(Sum_{k>=0} round((k+1)*r)(-x)^k), where r = 9/7.at n=17A289916