7823
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 7824
- Proper Divisor Sum (Aliquot Sum)
- 1
- 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
- 7822
- Möbius Function
- -1
- Radical
- 7823
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- yes
- Safe Prime
- yes
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 989
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Number of partitions of at most n into at most 5 parts.at n=33A002622
- 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 87.at n=24A031585
- Denominators of continued fraction convergents to sqrt(692).at n=11A042331
- Integers n such that A047988(n)=3.at n=37A047986
- Primes p such that there is no Carmichael number pqr, p<q<r q, r primes.at n=7A051663
- Least prime in A031924 (lesser of 6-twins) such that the distance to the next 6-twin is 2*n.at n=19A052352
- a(n) is smallest safe prime (A005385) such that a(n) + 12*n is the next safe prime, i.e., x = (a(n) - 1)/2 and x + 6*n are closest Sophie Germain primes.at n=17A059327
- Safe primes which are also Sophie Germain primes.at n=27A059455
- At stage 1, start with a unit equilateral equiangular triangle. At each successive stage add 3*(n-1) new triangles around outside with edge-to-edge contacts. Sequence gives number of triangles (regardless of size) at n-th stage.at n=25A064412
- Final terms of groups in A075639.at n=43A075642
- Primes p such that sum of even digits of p equals sum of odd digits of p.at n=35A076167
- a(n) = prime(n*(n+1)/2 + n).at n=42A078723
- First column of square array A082011.at n=44A082013
- p(k) such that 2*p(k)+3 and 2*p(k+1) + 3 are consecutive primes, where p(i) denotes the i-th prime.at n=31A089527
- Primes of the form prime(n)^2 - prime(n+1) - 1.at n=14A097938
- Primes of the form 23n+3.at n=43A100201
- Primes of the form 8*k-1 such that 4*k-1 and 16*k-1 are also primes.at n=15A101792
- Primes from merging of 4 successive digits in decimal expansion of cos(1).at n=31A104960
- Primes produced by a pyramidal ( three variable sequence) that is based on the Euler totient and multiperfect sigma functions.at n=20A117843
- Smaller of two consecutive Sophie Germain primes with the same digital sum.at n=20A118506