2421
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 9
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 3510
- Proper Divisor Sum (Aliquot Sum)
- 1089
- 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
- 1608
- Möbius Function
- 0
- Radical
- 807
- Omega Function (Ω)
- 3
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 19
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- Squares written in base 5.at n=19A001740
- Positions of remoteness 3 in Beans-Don't-Talk.at n=26A005695
- Coordination sequence T1 for Zeolite Code AET.at n=34A008007
- Coordination sequence T3 for Zeolite Code AET.at n=34A008009
- Coordination sequence T1 for Zeolite Code LAU.at n=35A008124
- Coordination sequence T1 for Zeolite Code MER.at n=36A008160
- Coordination sequence T1 for Zeolite Code NAT.at n=33A008203
- Coordination sequence T3 for Zeolite Code PAU.at n=36A008221
- Coordination sequence T6 for Zeolite Code PAU.at n=36A008224
- Molien series for A_5.at n=40A008628
- Number of compositions (p_1, p_2, p_3, ...) of n with 1 <= p_i <= i for all i.at n=14A008930
- Coordination sequence T2 for Zeolite Code -CHI.at n=31A009847
- For each permutation p of {1,2,...,n} define maxjump(p) = max(p(i) - i); a(n) is sum of maxjumps of all p.at n=5A018927
- Irreducible quadruple Euler sums of weight 2n+10 (verified for n <= 14).at n=49A019449
- Pseudoprimes to base 82.at n=35A020210
- a(n) = n*(15*n - 1)/2.at n=18A022272
- a(n) = Sum_{k=floor((n+1)/2)..n} T(k,n-k); i.e., a(n) is the n-th diagonal sum of left-justified array T given by A026998.at n=18A027010
- Numbers k such that k divides the (right) concatenation of all numbers <= k written in base 25 (most significant digit on right).at n=13A029518
- Number of bracelets (turnover necklaces) of n beads of 2 colors, 5 of them black.at n=25A032279
- Fractional part of square root of a(n) starts with 2: first term of runs.at n=46A034108