12121
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 7
- Digital Root
- 7
- Palindromic Number
- yes
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 13824
- Proper Divisor Sum (Aliquot Sum)
- 1703
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10560
- Möbius Function
- -1
- Radical
- 12121
- 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
- 143
- 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
- Primes in ternary.at n=35A001363
- Numbers that contain only 1's and 2's. Nonempty binary strings of length n in lexicographic order.at n=40A007931
- Pseudoprimes to base 70.at n=37A020198
- a(n) = n*(21*n-1)/2.at n=34A022278
- Poincaré (or Molien) series for ring of Siegel modular forms of genus 3 (associated with full modular group Gamma_3).at n=47A027634
- Two-bell analog of A028355.at n=6A028359
- Odd palindromes in which parity of digits alternates.at n=35A030148
- Palindromic lucky numbers.at n=32A031161
- Lucky numbers that are both palindromic and nonprime.at n=26A031880
- Composite numbers k, not a power of 2, such that the E(k) == 1 (mod k), where E(k) is the k-th Euler number (A000364).at n=35A035163
- Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 1,2.at n=4A037487
- Number of partitions satisfying 0 < cn(0,5) + cn(2,5) + cn(3,5).at n=34A039899
- Denominators of continued fraction convergents to sqrt(525).at n=7A042005
- Denominators of continued fraction convergents to sqrt(759).at n=10A042463
- Composite palindromes whose sum of prime factors is prime (counted with multiplicity).at n=36A046365
- Matrix 6th power of partition triangle A008284.at n=46A050300
- Coefficients of monic irreducible polynomials over GF(3) listed in lexicographic order.at n=30A058944
- Numbers k such that k and its reversal are both multiples of 17.at n=39A062906
- Coefficients of irreducible polynomials over GF(3) listed in lexicographic order.at n=33A065020
- The zero-free, right-to-left factorial walk encoding for each rooted plane tree encoded by A014486. Sequence A071155 shown with factorial expansion (A007623).at n=39A071157