12639
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 18432
- Proper Divisor Sum (Aliquot Sum)
- 5793
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7640
- Möbius Function
- -1
- Radical
- 12639
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- 200
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- G.f.: x^2*(x^2 + x + 1)/(x^4 - 2*x + 1).at n=14A027084
- a(n) is the number of subsequences {s(k)} of {1,2,3,...n} such that s(k+1)-s(k) is 1 or 3.at n=20A050228
- A Collatz-Fibonacci mixture: a(1) = 1, a(2) = 2, a(n+2) = a(n+1)/2+a(n)/2 if a(n+1) and a(n) have the same parity, a(n+2) = a(n+1)+a(n) otherwise.at n=38A069202
- Let r_1 = 1. Let r_{m+1} = r_1 + 1/(r_2 + 1/(r_3 +...(r_{m-1} + 1/r_m)...)), a continued fraction of rational terms. Then a(n) is the number of (positive integer) terms in the simple continued fraction of r_n.at n=16A138743
- Square root of squares in A145768 (XOR of squares of the numbers 1..n).at n=34A145829
- Expansion of Product_{k > 0} (1 + A147665(k)*x^k).at n=28A147871
- Numbers k such that the string k modulo 1000 is found at position k in the decimal digits of Pi.at n=35A153226
- Expansion of (1 + x + x^2)/(1 - x^2 - 2*x^3).at n=23A159288
- Expansion of (1-x+19*x^3-3*x^4)/(1-x)^3.at n=41A195241
- a(n) = (prime(n) - 1)*(prime(n+1) - 1)/2 + 3.at n=36A201498
- Values of n such that n^2 + d^2 is prime for a record first value of d.at n=15A239388
- Denominator of fraction equal to the continued fraction [2,7,1,8,2,...] (first n digits of e).at n=7A251626
- Numbers m, such that the smallest prime factor of 1+78557*2^m doesn't belong to the covering set {3, 5, 7, 13, 19, 37, 73}.at n=36A258095
- Solution of the complementary equation a(n) = 2*a(n-1) - a(n-2) + b(n-1) -1, where a(0) = 1, a(1) = 2, b(0) = 3, and (a(n)) and (b(n)) are increasing complementary sequences.at n=39A294867
- Numbers k such that A326057(k) is equal to A252748(k) and A252748(k) is not 1.at n=8A326134
- Odd numbers k for which A003961(k)-2k divides A003961(k)-sigma(k), where A003961 shifts the prime factorization one step towards larger primes, and sigma is the sum of divisors function.at n=12A349753
- G.f. satisfies A(x) = 1 + x * (1 + x^2)^2 * A(x * (1 + x^2)).at n=12A360888
- Numbers k such that (A003961(k)-2*k) divides (A003961(k)-sigma(k)), where A003961 is fully multiplicative with a(prime(i)) = prime(i+1), and sigma is the sum of divisors function.at n=27A378980
- Numbers k such that A003961(k) = 2k +- 7, multiplied by the sign of difference A003961(k)-2k, where A003961 is fully multiplicative with a(prime(i)) = prime(i+1).at n=10A379237