6421
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 6422
- 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
- 6420
- Möbius Function
- -1
- Radical
- 6421
- 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
- 23
- 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
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 835
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- From a Goldbach conjecture: records in A185091.at n=39A002092
- Truncated square numbers: 7*n^2 + 4*n + 1.at n=30A005892
- Primes that remain prime through 3 iterations of function f(x) = 3x + 10.at n=37A023280
- n written in fractional base 8/6.at n=25A024648
- s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n-k+1), where k = [ n/2 ], s = (composite numbers).at n=27A025102
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 60 ones.at n=6A031828
- Primes with distinct digits in descending order.at n=32A052014
- Primes from products of split even-digit primes.at n=29A053008
- a(1) = 2; a(n) is smallest prime > 2*a(n-1).at n=11A055496
- a(n) = p is the smallest prime such that p = n + h(n)^2 and p is the first prime following h(n)^2. The smallest immediate post-square primes with distance n = p - h(n)^2.at n=20A058056
- McKay-Thompson series of class 38a for Monster.at n=40A058658
- Primes p such that p^10 reversed is also prime.at n=30A059703
- A list of equal temperaments (equal divisions of the octave) whose nearest scale steps are closer and closer approximations to the ratios of 8 musical tones: 8/7 16/11 5/4 4/3 3/2 8/5 11/8 7/4.at n=36A060527
- a(2n) = concatenation of 4n+1 and 4n+2, a(2n+1) = concatenation of the two most nearly equal numbers whose product is a(2n).at n=13A068517
- a(1)=1, a(n)=2a(n-1)+1 if a(n-1) is prime, a(n)=a(n-1)+1 otherwise.at n=44A083005
- Primes that are a sum of twin primes and their indices.at n=24A088187
- Primes p such that (p-11)/10 is also a prime.at n=29A089442
- Leading diagonal of triangle A093922.at n=32A093923
- First of 9 consecutive primes in a 3 X 3 spiral wherein the mean of all 8 sums is prime.at n=23A094454
- a(1) = 2; k(1) = 0; for n > 1: k(n) = smallest number j >= k(n-1) such that 2*a(n-1) + j is prime; a(n) = 2*a(n-1) + k(n).at n=11A105120