15645
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 28800
- Proper Divisor Sum (Aliquot Sum)
- 13155
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7104
- Möbius Function
- 1
- Radical
- 15645
- Omega Function (Ω)
- 4
- Little Omega Function (ω)
- 4
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
- 84
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- Obtainable by applying +, * and exponentiation to its own digits.at n=23A046469
- T(n,n-5), where T is the array in A055830.at n=19A055832
- McKay-Thompson series of class 26a for Monster.at n=30A058598
- "Orderly" Friedman numbers (or "good" or "nice" Friedman numbers): Friedman numbers (A036057) where the construction digits are used in the proper order.at n=33A080035
- Number of distinct prime factors of the n-th odd Catalan number, A038003(n).at n=16A119861
- 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, -1, 1), (-1, 0, 0), (0, 0, -1), (0, 1, 1), (1, -1, 1)}.at n=9A148836
- Integers N such that by inserting + or - or * or / or ^ between each of their digits, without any grouping parentheses, you can get N (the ambiguous a^b^c is avoided).at n=9A156954
- Integers n such that by inserting between their digits + or - or * or / or ^ or nothing (i.e., concatenate two digits) you recover n back in a nontrivial way.at n=11A157198
- Numbers k such that k-4, k-2, k+2 and k+4 are prime.at n=13A173037
- Product of tribonacci numbers: a(n) = A000073(n+2)*A000213(n).at n=9A200543
- Triangle T(n,k), read by rows, given by (2, 1/2, -1/2, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (2, -1/2, -1/2, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938.at n=40A210637
- Products p*q*r*s of distinct primes for which (p*q*r*s + 1)/2 is prime.at n=33A234501
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 414", based on the 5-celled von Neumann neighborhood.at n=33A272014
- a(n) = 123*2^n - 99.at n=7A305160
- a(n) = n*(2*n - 3 - (-1)^n)*(5*n - 2 + (-1)^n)/16.at n=29A308025
- Aggregate values of n-th stage of growth for two-dimensional cellular automaton defined by "Rule 614", based on the 5-celled von Neumann neighborhood, calculated via even-zeroing instead of mod 2.at n=17A323110
- Triangle read by rows T(n, k) = Sum_{h>=0} Bernoulli(h)*binomial(k+h-1, h)*abs(Stirling1(n, h+k))*n^h for n>=0 and 0<=k<=n.at n=50A339207
- Number of solutions to 1 +-*/ 2 +-*/ 3 +-*/ ... +-*/ n = 0.at n=15A342804
- Expansion of e.g.f. A(x) satisfying A(x) = Sum_{n>=0} (A(x)^n + 4)^n * x^n/n!.at n=4A361055
- Exponents k where A000120(3^k) - A070939(3^k)/2 reaches a new minimum.at n=37A372097