2641
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2800
- Proper Divisor Sum (Aliquot Sum)
- 159
- 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
- 2484
- Möbius Function
- 1
- Radical
- 2641
- 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
- 102
- 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
- Genus of modular group Gamma(n) = genus of modular curve Chi(n).at n=44A001767
- a(0) = 1, a(1) = 0, a(2) = -1; for n >= 3, a(n) = - a(n-2) + Sum_{ primes p with 3 <= p <= n} a(n-p).at n=49A002121
- Pseudo-squares: a(n) = the least nonsquare positive integer which is 1 mod 8 and is a (nonzero) quadratic residue modulo the first n odd primes.at n=4A002189
- Numbers of the form (p^2 - 49)/120 where p is prime.at n=51A002382
- Number of nonequivalent dissections of an n-gon into 3 polygons by nonintersecting diagonals up to rotation and reflection.at n=36A003453
- Number of column-convex polyominoes with perimeter 2n+2.at n=6A005435
- Centered pentagonal numbers: (5n^2+5n+2)/2; crystal ball sequence for 3.3.3.4.4. planar net.at n=32A005891
- Expansion of 1/sqrt(1 - 10*x + x^2).at n=4A006442
- Euler characteristic of mapping class group Gamma_n.at n=12A007888
- Crystal ball sequence for planar net 4.8.8.at n=44A008577
- Expansion of e.g.f.: exp(sinh(x)/cos(x)).at n=7A009234
- Coordination sequence T3 for Zeolite Code iRON.at n=36A009883
- Pseudoprimes to base 96.at n=15A020224
- Strong pseudoprimes to base 96.at n=3A020322
- Numbers k such that the continued fraction for sqrt(k) has period 82.at n=2A020421
- a(n) = least m such that if r and s in {1/1, 1/4, 1/7,..., 1/(3n-2)} satisfy r < s, then r < k/m < s for some integer k.at n=34A024822
- Expansion of Product_{m>=1} (1+q^m)^(m^2).at n=9A027998
- Number of composite labeled T_0 topologies on n points.at n=4A028848
- a(n) = 5^n mod 2^n.at n=12A029757
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 34 ones.at n=6A031802