7820
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 17
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 24
- Divisor Sum
- 18144
- Proper Divisor Sum (Aliquot Sum)
- 10324
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 2816
- Möbius Function
- 0
- Radical
- 3910
- Omega Function (Ω)
- 5
- Little Omega Function (ω)
- 4
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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 101
- 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
- yes
- Odd
- no
Appears in sequences
- 4-dimensional pyramidal numbers: a(n) = (3*n+1)*binomial(n+2, 3)/4. Also Stirling2(n+2, n).at n=15A001296
- Stirling numbers of second kind S2(17,n).at n=14A011566
- Number of partitions of 5n such that cn(1,5) = cn(4,5) <= cn(0,5) < cn(2,5) = cn(3,5).at n=11A036885
- a(n) = Sum{a(k): k=0,1,2,...,n-4,n-2,n-1}; a(n-3) is not a summand; initial terms are 0,2,3.at n=15A049861
- a(n) = solution to the postage stamp problem with 7 denominations and n stamps.at n=10A053346
- a(n) is the number of solutions to x+y+z = 0 mod 3, where 1 <= x < y < z <= n.at n=53A061866
- Sum of first n 5-almost primes.at n=30A086047
- Sequence resulting from a sum of three repeated binomial(n+3,4) sequences.at n=28A093039
- E.g.f. exp(x)*(x^2+x+2)/(1-x).at n=6A107283
- Riordan array (1/(1-xc(2x)),xc(2x)/(1-xc(2x))), c(x) the g.f. of A000108.at n=40A110506
- An invertible triangle of ratios of triple factorials.at n=41A112333
- Riordan array (1/(1+xc(-2x)), xc(-2x)/(1+xc(-2x))), c(x) the g.f. of A000108.at n=40A114189
- Column 3 of triangle in A133721.at n=45A133722
- 10 times pentagonal numbers: a(n) = 5*n*(3*n-1).at n=23A153780
- a(n) = 250*n - 180.at n=32A154360
- Numbers k such that 1 + 3*10^k + 100^k is prime.at n=20A171376
- Denominators of fractions with the same position in A020652/A038567 and A182972/A182973.at n=12A182976
- Least common multiple of reversals of divisors of n in decimal representation.at n=57A188649
- Expansion of 1/((1-x)^5*(x^2+x+1)^3).at n=42A189374
- Coefficient of x in the reduction by x^2->x+1 of the polynomial p(n,x) defined at Comments.at n=11A193041