9191
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 11424
- Proper Divisor Sum (Aliquot Sum)
- 2233
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7200
- Möbius Function
- -1
- Radical
- 9191
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- 60
- 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
- Triangle of q-binomial coefficients for q=-10.at n=12A015123
- Gaussian binomial coefficient [ n,2 ] for q = -10.at n=2A015261
- Numbers whose consecutive digits differ by 8.at n=18A048410
- (Terms in A028286)/2.at n=33A051359
- Geometric mean of the digits = 3. In other words, the product of the digits is = 3^k where k is the number of digits.at n=26A061427
- Numbers, not composed of the same digits, such that the geometric and arithmetic means of their decimal digits are integers.at n=42A067452
- Generalized centered polygonal numbers.at n=13A081282
- An interleaved sequence of pyramidal and polygonal numbers.at n=25A081284
- a(n) is the smallest nonprime k such that tau(k + n) = tau(k) + n , where tau(n) is the number of divisors of n (A000005).at n=24A099642
- Numbers not of the form a^2 + b^3 + c^4 + d^5 for a,b,c,d >= 0.at n=20A111151
- Numbers n such that A064168(n) is prime.at n=63A123538
- Numbers k such that k and k^2 use only the digits 1, 4, 7, 8 and 9.at n=11A137058
- Partial sums of A027444.at n=13A152457
- Products of 3 distinct non-Sophie Germain primes.at n=36A157347
- a(n) = 343*n - 70.at n=26A157374
- Numbers k that divide 10^(k+1)-1.at n=30A175203
- A175366(n^2).at n=40A175367
- a(n) is the least number not occurring earlier such that neighboring digits sum to 1 or 10.at n=16A182396
- a(n) = Sum_{k=1..n} lcm(k,k')/gcd(k,k'), where n' is arithmetic derivative of n.at n=49A190120
- Divisors of the repunit 111111111111 = A002275(12).at n=38A197318