15212
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 11
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 26628
- Proper Divisor Sum (Aliquot Sum)
- 11416
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7604
- Möbius Function
- 0
- Radical
- 7606
- 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
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 84
- 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 points on surface of cuboctahedron (or icosahedron): a(0) = 1; for n > 0, a(n) = 10n^2 + 2. Also coordination sequence for f.c.c. or A_3 or D_3 lattice.at n=39A005901
- Convolution of natural numbers n >= 1 with Lucas numbers L(k) for k >= -4.at n=20A033817
- a(n) is twice the smallest k such that A051686(k) = prime(n).at n=40A051692
- Twice the positions in A051686 at which new primes appear in that sequence.at n=42A051861
- Output of the linear congruential pseudo-random number generator used in function rand() as described in Kernighan and Ritchie, when seeded with 0.at n=18A096554
- a(0) = 1; for n>0, a(n) = (n+3)*2^(n-2)-n*binomial(n-1, floor( (n-1)/2 ))-(n-1)*binomial(n-2,floor((n-2)/2)).at n=13A121285
- Triangle, read by rows, that transforms diagonals in the array A158825 of coefficients of successive iterations of x*C(x) where C(x) is the Catalan function (A000108).at n=22A158835
- Column 1 of triangle A158835.at n=5A158837
- Number of permutations p of {1,...,n} such that exactly two elements of {p(1),...,p(i-1)} are between p(i) and p(i+1) for all i from 3 to n-1.at n=21A187817
- Start of n consecutive indices k such that phi(k) contains distinct number of divisors.at n=15A193901
- Number of partitions of n such that (number parts having multiplicity 1) is not a part and (number of 1s) is not a part.at n=43A241509
- Composite numbers k such that phi(x) = psi(k)*phi(k) has no solution.at n=6A292714
- Anagrexpo integers: integers N that exactly reproduce their set of digits when we form the set of exponentiation of pairs of adjacent digits, from left to right.at n=27A297627
- a(n) = Sum_{k=1..n} (-1)^(k+1) * floor(n/(2*k-1))^3.at n=24A350163