2123
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 8
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2328
- Proper Divisor Sum (Aliquot Sum)
- 205
- 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
- 1920
- Möbius Function
- 1
- Radical
- 2123
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
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
- no
- Composite Number
- yes
- Semiprime
- yes
- 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
- Positions of remoteness 5 in Beans-Don't-Talk.at n=41A005697
- Number of directed animals of size n (or directed n-ominoes in standard position).at n=9A005773
- Coordination sequence T4 for Zeolite Code NON.at n=28A008215
- Number of ordered triples of integers from [ 1,n ] with no common factors between pairs.at n=34A015632
- a(n) = (d(n)-r(n))/5, where d = A026043 and r is the periodic sequence with fundamental period (0,2,3,0,0).at n=28A026045
- How the astronomical clock ("Orloj") in Prague strikes the hours (digits follow 12343212343... (A028356), n-th group adds to n).at n=31A028354
- How the astronomical clock ("Orloj") in Prague strikes the hours (digits follow 12343212343... (A028356), n-th group adds to n).at n=7A028354
- How the astronomical clock ("Orloj") in Prague would strike 1,2,3,...,24,25,.. (digits follow 12343212343... (A028356), n-th group adds to n).at n=7A028355
- Triangle T(n,m) = Sum_{k=0..m} Catalan(n-k)*Catalan(k).at n=38A028364
- Triangle read by rows: T(n,m) = Sum Catalan(n-k)*Catalan(k), k=0..m.at n=48A028376
- Concatenate rows of triangle in A028364 (removing duplicates).at n=31A028378
- Numbers n such that n divides the (right) concatenation of all numbers <= n written in base 23 (most significant digit on right).at n=11A029516
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 45.at n=9A031543
- Concatenation of n and n + 2 or {n,n+2}.at n=20A032607
- Positive numbers having the same set of digits in base 5 and base 8.at n=22A037431
- Triangular array that counts rooted polyominoes.at n=36A038622
- a(n) = (s(n)+1)/7, where s(n) = n-th base 7 palindrome that starts with 6.at n=25A043064
- Numbers n such that string 1,3 occurs in the base 8 representation of n but not of n-1.at n=37A044198
- Numbers n such that string 1,8 occurs in the base 9 representation of n but not of n-1.at n=29A044268
- Numbers n such that string 2,3 occurs in the base 10 representation of n but not of n-1.at n=23A044355