2161
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 2162
- 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
- 2160
- Möbius Function
- -1
- Radical
- 2161
- 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
- 32
- 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
- 326
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Irregular table read by rows: row n lists prime factors of 10^n + 1, with multiplicity.at n=44A001271
- Number of n-stacks with strictly receding walls, or the number of Type A partitions of n in the sense of Auluck (1951).at n=29A001522
- Smallest primitive prime factor of Fibonacci number F(n), or 1 if F(n) has no primitive prime factor.at n=39A001578
- Primes of the form 2^q*3^r*5^s + 1.at n=41A002200
- Primes with record values of the least positive primitive root.at n=8A002230
- Primes of the form k^2 - k - 1.at n=26A002327
- Numbers k such that k*10^k + 1 is prime.at n=5A007647
- Number of nonsplit type 2 metacyclic 2-groups of order 2^n.at n=55A007981
- Coordination sequence T6 for Zeolite Code PAU.at n=34A008224
- Crystal ball sequence for A_9 lattice.at n=2A008394
- a(n) is prime and sum of all primes <= a(n) is prime.at n=31A013917
- Coordination sequence T2 for Zeolite Code CZP.at n=30A019457
- Numbers k such that the continued fraction for sqrt(k) has period 63.at n=1A020402
- Smallest prime having least positive primitive root n, or 0 if no such prime exists.at n=22A023048
- Primes that remain prime through 2 iterations of function f(x) = 4x + 3.at n=29A023250
- Primes that remain prime through 2 iterations of the function f(x) = 8*x + 5.at n=18A023262
- Primes that remain prime through 2 iterations of function f(x) = 10x + 3.at n=43A023269
- Numbers whose least quadratic nonresidue (A020649) is 7.at n=33A025023
- In base 11, a(n) = sum of digits of Lucas(a(n)).at n=27A025491
- Sum of numbers between the two n's in A026272.at n=43A026275