9091
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 9092
- Proper Divisor Sum (Aliquot Sum)
- 1
- 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
- 9090
- Möbius Function
- -1
- Radical
- 9091
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- 140
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 1128
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/5.at n=23A001135
- Table of prime factors of 10^n - 1 (with multiplicity).at n=45A001270
- Irregular table read by rows: row n lists prime factors of 10^n + 1, with multiplicity.at n=45A001271
- Irregular table read by rows: row n lists prime factors of 10^n + 1, with multiplicity.at n=9A001271
- Quintan primes: p = (x^5 + y^5)/(x + y).at n=13A002650
- Largest prime factor of the "repunit" number 11...1 (cf. A002275).at n=8A003020
- Largest prime factor of 10^n + 1.at n=5A003021
- Largest prime factor of 10^n + 1.at n=15A003021
- Largest prime factor of 10^n - 1.at n=9A005422
- a(n) = largest prime factor of n^n - 1.at n=8A006486
- Smallest primitive factor of 10^n - 1. Also smallest prime p such that 1/p has repeating decimal expansion of period n.at n=9A007138
- Primes with unique period length (the periods are given in A007498).at n=5A007615
- a(n) = (1 - (-10)^n)/11.at n=4A014992
- Triangle of q-binomial coefficients for q=-10.at n=19A015123
- Triangle of q-binomial coefficients for q=-10.at n=16A015123
- Gaussian binomial coefficient [ n,4 ] for q = -10.at n=1A015298
- a(n) = 9*a(n-1) + 10*a(n-2).at n=5A015585
- Cyclotomic polynomials at x=10.at n=9A019328
- Cyclotomic polynomials at x=-10.at n=5A020509
- Primes that remain prime through 3 iterations of function f(x) = 4x + 9.at n=24A023282