15987
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 30
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 21612
- Proper Divisor Sum (Aliquot Sum)
- 5625
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10512
- Möbius Function
- 0
- Radical
- 219
- 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
- no
- Odd
- yes
Appears in sequences
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 84.at n=32A031582
- Numbers that are the product of 3 prime factors whose concatenation is a palindrome.at n=35A046452
- 3p^2 where p runs through the primes.at n=20A079705
- G.f.: A(x) = exp(sum(n>=1, A084250(n)*x^n/n)), where A084250 lists the least distinct positive integers that allow A(x) to be an integer power series.at n=36A084251
- Composite numbers n such that 8*n^2-2*n-1 divides the primitive part U(n) of Fibonacci(n).at n=32A159234
- Numbers of the form 20*k+7 which are three times a square.at n=14A192328
- Numbers k such that 2*(3^k-k)-1 is prime.at n=15A195732
- 3*h^2, where h is an odd integer not divisible by 3.at n=24A229852
- The sum of the totatives of n is a perfect cube.at n=28A237282
- Number of partitions of n*(n-1)/2 into at most three parts.at n=29A274233
- Numbers that are the sum of three squares in arithmetic progression.at n=28A292313
- a(n) = Sum_{k=1..n} sigma(k)*sigma(2*k), where sigma(n) = A000203(n) is the sum of the divisors of n.at n=18A347108
- Numbers of the form p^2*q, with odd primes p > q, such that q divides p-1.at n=14A350638
- a(n) is the number of complement pairs of imprimitive (periodic) 2n-bead balanced binary necklaces.at n=33A387130
- The maximal norm of an additively indecomposable element in Shanks' simplest cubic field Q[x]/(x^3 - n*x^2 - (n+3)*x - 1).at n=24A387575
- Numbers k such that sigma(k) = psi(k) + omega(k)^2.at n=50A390251