6521
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 14
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 6522
- 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
- 6520
- Möbius Function
- -1
- Radical
- 6521
- 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
- 181
- 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
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 843
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Coefficient of q^(2n-1) in the series expansion of Ramanujan's mock theta function f(q).at n=41A000199
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/4.at n=38A001134
- Number of compositions of n into a sum of odd primes.at n=40A002124
- Primes p == 1 (mod 8), p = a^2 +64*b^2 such that y^2 = x^3 + p*x has rank 0.at n=30A007765
- Numbers k such that the continued fraction for sqrt(k) has period 81.at n=4A020420
- Number of partitions of n into 9 unordered relatively prime parts.at n=35A023029
- Primes that are palindromic in base 6.at n=21A029974
- Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 14.at n=6A031602
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 38 ones.at n=33A031806
- Write 1,2,... in a clockwise spiral; sequence gives numbers on positive x axis.at n=40A033951
- Expansion of Sum_{n>=0} (q^n / Product_{k=1..n+5} (1 - q^k)).at n=26A035301
- Base-6 palindromes that start with 5.at n=15A043014
- Numbers k such that sum of factorials of digits of k equals pi(k) (A000720).at n=4A049529
- Primes with distinct digits in descending order.at n=33A052014
- Fifth term of weak prime quintets: p(m-3)-p(m-4) < p(m-2)-p(m-3) < p(m-1)-p(m-2) < p(m)-p(m-1).at n=16A054827
- Primes p for which the period of reciprocal = (p-1)/8.at n=13A056213
- Primes p such that x^24 = 2 has no solution mod p, but x^12 = 2 has a solution mod p.at n=32A059331
- Primes p such that x^56 = 2 has no solution mod p, but x^28 = 2 has a solution mod p.at n=39A059635
- Primes on axis of Ulam square spiral (with rows ... / 7 8 9 / 6 1 2 / 5 4 3 / ... ) with origin at (1).at n=38A078784
- a(n) = smallest prime > n*prime(n).at n=38A079779