8021
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 11
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 8652
- Proper Divisor Sum (Aliquot Sum)
- 631
- 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
- 7392
- Möbius Function
- 1
- Radical
- 8021
- 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
- 114
- 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
- a(0) = 1, a(n) = 11*n^2 + 2 for n>0.at n=27A010003
- Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted then there are a pair of central terms both equal to 7.at n=22A031420
- (s(n)+2)/10, where s(n)=n-th base 10 palindrome that starts with 8.at n=24A043087
- Numbers whose base-6 representation has exactly 6 runs.at n=19A043614
- Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 5.at n=15A051970
- Multiplicity of irreducible character IRR2 of Monster simple group in n-th head character.at n=29A055771
- Sum of distinct powers of 20; i.e., numbers with digits in {0,1} base 20; i.e., write n in base 2 and read as if written in base 20.at n=11A063012
- Smallest k>n such that n^3+1 divides k*n^2+1.at n=20A071568
- a(1) = 4 and then least composite such that every partial concatenation of 2 or more terms is a prime.at n=45A086474
- Sum of primitive roots of n-th prime.at n=42A088144
- Number of partitions of the n-th abundant number into abundant numbers.at n=53A097800
- Numbers NM associated with A107677.at n=1A107678
- Sequence obtained using characteristic polynomial that is Laplace transform of the tribonacci characteristic polynomial: -s^4*L(t^3 -t^2 -t -1) = s^3 +s^2 +2*s -6.at n=13A107785
- Numbers whose square is the concatenation of two numbers k and k+8.at n=1A115440
- Antidiagonal sums of triangle A118180: a(n) = Sum_{k=0..[n/2]} (3^k)^(n-2*k) for n>=0.at n=8A118182
- a(0)=1, a(1)=2, a(2)=3, a(3)=5, a(4)=7, a(5)=10; a(n) = floor(a(n-1) + 1 + a(n-2)/6) for n>=6.at n=52A119565
- Write 0, 1, ..., n in base 3 and add as if they were decimal numbers.at n=31A121718
- a(n) = 3*A146085(n) - 1.at n=45A146087
- Numbers k such that continued fraction of (1 + sqrt(k))/2 has period 5.at n=44A146330
- (n-1)^(p-n+1)+n where p is the smallest prime > n-1.at n=20A171424