8129
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
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 8880
- Proper Divisor Sum (Aliquot Sum)
- 751
- 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
- 7380
- Möbius Function
- 1
- Radical
- 8129
- 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
- 39
- 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
- Numbers k such that the continued fraction for sqrt(k) has period 84.at n=22A020423
- Fibonacci sequence beginning 2, 7.at n=16A022113
- Convolution of Lucas numbers and A000201.at n=13A023621
- a(n) = T(2n-1,n-1), T given by A026769. Also T(2n+1,n+1), T given by A026780.at n=6A026773
- a(n) = T(n, floor(n/2)), T given by A026769.at n=13A026775
- Greatest number in row n of array T given by A026769.at n=13A027238
- a(n)=T(n,n+2), array T as in A049735.at n=35A049742
- Truncated triangular pyramid numbers: a(n) = Sum_{k=4..n} (k*(k+1)/2 - 9).at n=32A051937
- a(n) = (9n^2 + 9n + 4)/2.at n=42A062123
- a(n) = (-1)^(n+1) * coefficient of x^n in Sum_{k>=1} x^k/(1+2*x^k).at n=13A081295
- Numbers k such that k, k+2, k+4, k+6, k+8, k+10, k+12 and k+14 are semiprimes.at n=0A082919
- Members of A000124 which are multiples of 11.at n=23A083511
- Numbers k such that k, k+2, k+4, k+6, k+8 are semiprimes.at n=23A092127
- Numbers k such that k, k+2, k+4, k+6, k+8, k+10 are semiprimes.at n=4A092128
- Numbers k such that k, k+2, k+4, k+6, k+8, k+10, k+12 are semiprimes.at n=1A092129
- Duplicate of A082919.at n=0A092208
- Smallest number k such that k, k+2, k+4, ..., k+2n are semiprimes.at n=7A092209
- a(0)=2, a(1)=5, a(n+2) = a(n+1) + (-1)^n a(n).at n=35A095795
- a(0)=2, a(1)=5, a(n+2) = a(n+1) + (-1)^n a(n).at n=32A095795
- Counterexamples to the conjecture that an even, prime-indexed triangular plus 1 equals a prime or that an odd, prime-indexed triangular minus 2 equals a prime.at n=9A097785