7851
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
- 4
- Divisor Sum
- 10472
- Proper Divisor Sum (Aliquot Sum)
- 2621
- 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
- 5232
- Möbius Function
- 1
- Radical
- 7851
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 83
- 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
- Expansion of 1/((1-x)(1-5x)(1-7x)).at n=4A016230
- 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 29.at n=32A031527
- Numbers whose base-4 representation contains exactly four 2's and two 3's.at n=25A045155
- Integers n > 879 such that the 'Reverse and Add!' trajectory of n joins the trajectory of 879.at n=41A063052
- Positions of sevens (ground states) in A084451.at n=17A084449
- Expansion of ((eta(q^2) * eta(q^14)) / (eta(q) * eta(q^7)))^3 in powers of q.at n=17A120006
- Expansion of eta(q^4) * eta(q^28) / (eta(q) * eta(q^7)) in powers of q.at n=35A123648
- A 4 X 4 permutation-free magic square with magic sum 19998.at n=8A125522
- a(n) = (n^3)/2 + (3*n^2)/2 + 3*n + 3.at n=23A127873
- G.f. A(x) satisfies A(x/A(x)^2) = 1/(1-x)^3.at n=4A145169
- 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, 1, 1), (1, 0, -1), (1, 1, 0)}.at n=8A149158
- 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, 0, 0), (-1, 0, 1), (0, -1, 0), (0, 1, -1), (1, 1, 0)}.at n=8A149326
- a(n) = Sum_{d|n} d*binomial(n/d+d-2,d-1).at n=39A157020
- 2*A197072(n-1) - A197072(n).at n=19A197100
- Number of 4-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero with no three beads in a row equal.at n=21A209345
- Number of (n+1) X (1+1) 0..1 arrays with no element having a strict majority of its horizontal, vertical and antidiagonal neighbors equal to one.at n=7A231703
- T(n,k)=Number of (n+1)X(k+1) 0..1 arrays with no element having a strict majority of its horizontal, vertical and antidiagonal neighbors equal to one.at n=28A231710
- T(n,k)=Number of (n+1)X(k+1) 0..1 arrays with no element having a strict majority of its horizontal, vertical and antidiagonal neighbors equal to one.at n=35A231710
- Number of partitions p of n such that median(p) = multiplicity(max(p)).at n=39A240209
- a(n) = floor(4^n/(2+2*cos(2*Pi/7))^n).at n=43A240671