6921
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 10010
- Proper Divisor Sum (Aliquot Sum)
- 3089
- 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
- 4608
- Möbius Function
- 0
- Radical
- 2307
- 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
- no
- Narcissistic Number
- no
- Collatz Steps
- 75
- 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
- 4th powers written backwards.at n=5A002108
- a(n) = n^2 written backwards.at n=35A002942
- Expansion of log(1+log(1+x)/cosh(x)).at n=7A009323
- Expansion of log(1+x/cosh(x)).at n=9A009443
- Pisot sequence E(3,11), a(n) = floor(a(n-1)^2/a(n-2) + 1/2).at n=6A010911
- E.g.f.: log(cosh(x)+log(x+1)).at n=7A013185
- Numbers k such that the continued fraction for sqrt(k) has period 62.at n=28A020401
- Number of partitions of n into parts not of form 4k+2, 16k, 16k+5 or 16k-5.at n=50A036022
- Number of nonprimes <= prime(n)^2.at n=23A053683
- Composites for which the row of the prime-composite array (A063173) includes the leftmost element of both a zero-only antidiagonal and a zero-only diagonal(A067681).at n=42A063176
- Numbers n such that [A070080(n), A070081(n), A070082(n)] is an isosceles integer triangle with integer area.at n=19A070145
- Numbers n such that [A070080(n), A070081(n), A070082(n)] is an acute integer triangle with integer area.at n=20A070146
- Powers of 6 written backwards.at n=4A071588
- n^2 read backwards, for n = 51, 50, 49, ..., 1.at n=15A080334
- a(n) = 3*a(n-1) + 2*a(n-2) + a(n-3).at n=8A108153
- Least number k>1 such that k+10^n is a symmetric prime with symmetric digits (i.e. such that k+10^n is in A007500).at n=48A122490
- Powers of 6 written backwards and sorted.at n=5A134112
- Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, -1), (-1, -1, 0), (-1, 0, 1), (1, -1, -1), (1, 1, 0)}.at n=9A148606
- Numbers which are a difference of two of their own anagrams.at n=41A160851
- Distance of the least reversible n-digit prime from 10^(n-1).at n=49A168159