9901
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
- 9902
- 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
- 9900
- Möbius Function
- -1
- Radical
- 9901
- 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
- 73
- 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
- 1221
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Table of prime factors of 10^n - 1 (with multiplicity).at n=58A001270
- Irregular table read by rows: row n lists prime factors of 10^n + 1, with multiplicity.at n=11A001271
- Primes of form k^2 + k + 1.at n=31A002383
- Sextan primes: p = (x^6 + y^6)/(x^2 + y^2).at n=19A002647
- Largest prime factor of the "repunit" number 11...1 (cf. A002275).at n=10A003020
- Largest prime factor of 10^n + 1.at n=6A003021
- Largest prime factor of 10^n - 1.at n=11A005422
- Smallest primitive factor of 10^n - 1. Also smallest prime p such that 1/p has repeating decimal expansion of period n.at n=11A007138
- Primes with unique period length (the periods are given in A007498).at n=6A007615
- Apply partial sum operator twice to Catalan numbers.at n=9A014140
- Cyclotomic polynomials at x=10.at n=11A019328
- Numbers k such that the continued fraction for sqrt(k) has period 33.at n=26A020372
- Cyclotomic polynomials at x=-10.at n=12A020509
- Multiplicity of highest weight (or singular) vectors associated with character chi_15 of Monster module.at n=38A034403
- Primes p such that (p+1)/2 and (p+2)/3 are also primes.at n=25A036570
- Prime 3 followed by unique period primes (the period r of 1/p is not shared with any other prime) of the form A019328(r)/gcd(A019328(r),r) in order (periods r are given in A051627).at n=5A040017
- Triangle of prime numbers in which n-th row lists all primes p such that 1/p has decimal period n, n >= 1.at n=16A046107
- Numbers m such that m^2 is a concatenation of two consecutive decreasing numbers.at n=2A054216
- Numbers k such that 2*3^k - 5 is prime.at n=21A057910
- Smallest primitive prime factor of the n-th Lucas number (A000032); i.e., L(n), L(0) = 2, L(1) = 1 and L(n) = L(n-1) + L(n-2).at n=33A058036