7991
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 26
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 8184
- Proper Divisor Sum (Aliquot Sum)
- 193
- 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
- 7800
- Möbius Function
- 1
- Radical
- 7991
- 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
- 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
- Convolution of partition numbers and Catalan numbers.at n=9A014329
- Pseudoprimes to base 58.at n=32A020186
- Pseudoprimes to base 70.at n=33A020198
- Strong pseudoprimes to base 58.at n=9A020284
- a(n+1) = a(n) converted to base 7 from base 6 (written in base 10).at n=28A023384
- Decimal part of n-th root of a(n) starts with digit 9.at n=12A034086
- Integers n > 1997 such that the 'Reverse and Add!' trajectory of n joins the trajectory of 1997.at n=4A063055
- n*10^5-1, n*10^5-3, n*10^5-7 and n*10^5-9 are all prime.at n=2A064979
- Smallest k such that k^3 -1 is a squarefree number with n prime divisors. a(n) = A088029(n)^(1/3).at n=8A088030
- Index of the first occurrence of prime(n) in A092938.at n=40A092939
- a(n) = 6*n*(n-1) - 1.at n=37A103115
- Integer part of 5th root of product of first n primes.at n=15A127602
- Number of nonempty subsets of {1, 2, ..., n} with <=9 pairwise coprime elements.at n=23A187270
- a(n) = n*(7*n + 11)/2 + 1.at n=47A198017
- Least number m such that phi(m-6n) = phi(m) = phi(m+6n) and m is not divisible by n.at n=0A217068
- Numbers n such that phi(n) = phi(n+12) and n is not divisible by 2.at n=22A217141
- Number of n X 2 arrays of the minimum value of corresponding elements and their horizontal or vertical neighbors in a random, but sorted with lexicographically nondecreasing rows and nonincreasing columns, 0..2 n X 2 array.at n=17A219589
- Number of partitions of n such that the number of parts having multiplicity >1 is not a part and the number of distinct parts is a part.at n=42A241410
- Number of 3Xn arrays containing n copies of 0..3-1 with no element 1 greater than its north, west, northwest or southwest neighbor modulo 3 and the upper left element equal to 0.at n=11A266826
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 245", based on the 5-celled von Neumann neighborhood.at n=22A271006