6861
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
- 4
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 9152
- Proper Divisor Sum (Aliquot Sum)
- 2291
- 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
- 4572
- Möbius Function
- 1
- Radical
- 6861
- 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
- 31
- 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
- a(0) = 1, a(n) = 19*n^2 + 2 for n>0.at n=19A010009
- Numbers k such that the continued fraction for sqrt(k) has period 94.at n=10A020433
- Number of 3's in n-th term of A007651.at n=37A022468
- a(n) = [ a(n-1)/a(1) ] + [ a(n-3)/a(3) ] + [ a(n-5)/a(5) ] + ..., for n >= 3.at n=33A022878
- 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 54.at n=36A031552
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 40 ones.at n=31A031808
- a(n) = (n-1)*(n-2)*(n-3) + n.at n=20A034324
- Expansion of 1/(1-x)^2/(1-x^2)/(1-x^3)/(1-x^5)/(1-x^8).at n=36A034379
- a(n)=T(n,n+2), array T as in A049735.at n=32A049742
- Numbers k such that k! is divisible by the square of (f+d)!^2 for d = 0, 1 and 2 (and possibly larger d), where f = floor(k/2).at n=31A056068
- Number of 7 X 7 binary matrices with n ones, with no zero rows or columns, up to row and column permutation.at n=31A056079
- Numbers n such that sigma(n-1) + sigma(n+1) = sigma(2n).at n=4A067730
- a(1) = 9, then the smallest number such that the forward as well as the reverse n-th partial concatenation is a prime for n>1. (Reverse concatenation is taken term-wise and not digit-wise).at n=32A083995
- a(n) = n^3 + 2.at n=19A084380
- Integers k such that nextprime(k^5) - prevprime(k^5) = 4.at n=6A090123
- Least k (or 0 if no such k exists) such that 10^n+k is the least bemirp of a quartet of 4 different bemirps and the least bemirp of n+1 digits.at n=4A122568
- Floor(Zeta(3)^n).at n=47A125890
- a(n) = 196*n + 1.at n=34A158223
- Numbers n with following property: let c = nearest cube to n that is different from n and let p = nearest prime to n that is different from n. Then |n-c| = |n-p|.at n=18A163497
- Number of permutations of length n which avoid the patterns 4213 and 3421.at n=8A165539