7891
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 8512
- Proper Divisor Sum (Aliquot Sum)
- 621
- 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
- 7272
- Möbius Function
- 1
- Radical
- 7891
- 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
- 101
- 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
- Blocks of increasing length using 1,2,3,...,9,10; omit leading 0's.at n=3A001369
- Number of achiral rooted trees.at n=23A003241
- Lengths increase by 1, digits cycle through positive digits.at n=3A007923
- Cycle class sequence c(n) (the number of true cycles of length n in which a certain node is included) for zeolite RUT = RUB-10 R4[B4Si32O72] starting from a T4 atom.at n=12A019231
- Number of 2's in n-th term of A022482.at n=33A022485
- Cube root of A030697.at n=16A030698
- Number of partitions satisfying cn(0,5) <= cn(1,5) + cn(4,5).at n=32A039839
- Denominators of continued fraction convergents to sqrt(649).at n=10A042247
- Semiprimes p1*p2 such that p2 mod p1 = 9, with p2 > p1.at n=41A064907
- Let N = 123456789101112131415161718..., the concatenation of the natural numbers. a(n) is the n-digit number formed from the digits of N starting from the {n(n-1)/2 +1}th digit. Omit any leading zeros.at n=3A066547
- Expansion of (7 +4*x -5*x^2 -7*x^3) / ((1-x)*(1-x^2-x^3)).at n=25A103485
- Slowest increasing sequence with its first 10 digits all different one from another, then the next 10, then the next 10, etc.at n=27A106604
- Numbers k such that 609 * 10^k - 1 is prime.at n=24A108320
- Number of partitions that are "2-close" to being self-conjugate.at n=44A108961
- G.f. = f(x), where f(x)^2 = o.g.f. for A088313 (with offset 0).at n=6A109777
- Start with 1 and repeatedly reverse the digits and add 35 to get the next term.at n=21A118632
- G.f.: (x^2+6*x^3+7*x^4+8*x^5+4*x^6-3*x^8-2*x^9-x^10) / ((1-x)^2*(1-x^2)^3*(1-x^3)^4*(1-x^4)).at n=12A127813
- Triangle read by rows: T(n,k) = value of the string of length k beginning at position n in the concatenation of natural numbers in decimal representation, 1<=k<=n.at n=24A162711
- Composite numbers such that exactly ten distinct permutations of digits are prime.at n=19A163562
- a(n) = n*(6*n^2 + 15*n + 5)/2.at n=13A163833