2639
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 3360
- Proper Divisor Sum (Aliquot Sum)
- 721
- 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
- 2016
- Möbius Function
- -1
- Radical
- 2639
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 146
- 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
- Coordination sequence for hyperbolic tessellation 3^7 (from triangle group (2,3,7)).at n=7A001354
- a(n) = floor(1000*log(n)).at n=13A004240
- a(n) = 1000*log(n) rounded to the nearest integer.at n=13A004241
- 9-gonal (or enneagonal) pyramidal numbers: a(n) = n*(n+1)*(7*n-4)/6.at n=13A007584
- Coordination sequence T2 for Zeolite Code SGT.at n=32A008230
- Coordination sequence T3 for Zeolite Code -CLO.at n=45A009852
- Coordination sequence T3 for Zeolite Code ZON.at n=36A009921
- Imaginary Rabbits: imaginary part of a(0)=i; a(1)=-i; a(n) = a(n-1) + i*a(n-2), with i = sqrt(-1).at n=27A014291
- Odd numbers k such that phi(k) | sigma_3(k).at n=41A015809
- Expansion of 1/(1-x^5-x^6-x^7-x^8-x^9).at n=41A017840
- Fibonacci sequence beginning 0, 7.at n=14A022090
- a(n) = n*(27*n - 1)/2.at n=14A022284
- Triangular array T read by rows: T(n,0) = 1 for n >= 0; T(1,1) = 1; and for n >= 2, T(n,k) = T(n-1,k-1) + T(n-1,k) for k = 1,2,...,[(n+1)/2]; T(n,n/2 + 1) = T(n-1,n/2) if n is even.at n=75A026009
- a(n) = number of (s(0), s(1), ..., s(2n)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 2, s(2n) = 4. Also a(n) = T(2n,n-1), where T is the array defined in A026009.at n=6A026013
- a(n) = (d(n)-r(n))/2, where d = A026054 and r is the periodic sequence with fundamental period (1,0,0,0).at n=26A026055
- Number of partitions of n into an odd number of parts, the least being 5; also, a(n+5) = number of partitions of n into an even number of parts, each >=5.at n=65A027191
- Coordination sequence T1 for Zeolite Code CGS.at n=38A027365
- Numbers whose base-3 representation has exactly 8 runs.at n=29A043588
- Numbers n such that number of runs in the base 3 representation of n is congruent to 0 mod 8.at n=29A043798
- Numbers n such that number of runs in the base 3 representation of n is congruent to 8 mod 9.at n=29A043814