6645
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 10656
- Proper Divisor Sum (Aliquot Sum)
- 4011
- 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
- 3536
- Möbius Function
- -1
- Radical
- 6645
- 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
- 137
- 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
- Largest number not the sum of distinct n-th-order polygonal numbers.at n=24A007419
- a(n) = T(n,2n-1), T given by A027023.at n=10A027050
- Decimal part of cube root of a(n) starts with 8: first term of runs.at n=17A034134
- Number of partitions satisfying (cn(0,5) <= cn(1,5) = cn(4,5)).at n=46A036809
- Numbers whose base-9 representation has exactly 5 runs.at n=2A043634
- Numbers k such that k^2 is formed from two subsquares that overlap in a single digit.at n=7A048422
- a(1) = 1; a(n+1) = n!*Sum_{k|n} a(k)/k!.at n=7A068100
- Interprimes which are of the form s*prime, s=15.at n=28A075290
- G.f.: (1+3*x^3)/((1-x)^2*(1-x^3)^2).at n=43A092352
- Rectangular table, read by antidiagonals, where the g.f. of row n is Sum_{i>=0} F_i(x)^n / 2^(i+1), where F_0(x)=x, F_{n+1}(x) = F_n(x+x^2), for n>=1.at n=33A122941
- Numbers n such that n^3 is zeroless pandigital.at n=28A124628
- Row sums of triangle A134310.at n=10A134311
- Numbers n such that 2*29^n + 1 is prime.at n=9A141802
- Row 4 of table A162424.at n=18A162427
- Number of lattice paths from (0,0) to (n,n) using steps (1,0), (1,1), (1,2), and (2,1).at n=9A191354
- G.f.: exp( Sum_{n>=1} (x^n/n) / Product_{d|n} (1 - d*x^n) ).at n=19A198296
- Number of nX3 arrays of the minimum value of corresponding elements and their horizontal, diagonal or antidiagonal neighbors in a random, but sorted with lexicographically nondecreasing rows and nonincreasing columns, 0..2 nX3 array.at n=7A219878
- T(n,k)=Number of nXk arrays of the minimum value of corresponding elements and their horizontal, diagonal or antidiagonal neighbors in a random, but sorted with lexicographically nondecreasing rows and nonincreasing columns, 0..2 nXk array.at n=52A219883
- Construct sequences P,Q,R by the rules: Q = first differences of P, R = second differences of P, P starts with 1,5,11, Q starts with 4,6, R starts with 2; at each stage the smallest number not yet present in P,Q,R is appended to R; every number appears exactly once in the union of P,Q,R. Sequence gives P.at n=29A225376
- Number of partitions of n for which 2*(number of distinct parts) > (number of parts).at n=36A237365