16657
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 16658
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 16656
- Möbius Function
- -1
- Radical
- 16657
- 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
- 66
- 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
- 1927
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Maximal number of states in the minimal deterministic finite automaton accepting a language over a binary alphabet consisting of some words of length n.at n=17A000802
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (natural numbers), t = (primes).at n=35A024867
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 72 ones.at n=26A031840
- Numbers whose set of base-16 digits is {1,4}.at n=22A032828
- Sums of 4 distinct powers of 4.at n=40A038472
- Numbers whose base-4 representation contains exactly four 0's and four 1's.at n=5A045037
- Numbers k such that 2^k + 21 is prime.at n=32A057201
- Primes which can be expressed as sum of distinct powers of 4.at n=19A077718
- Primes p such that p + 2^2, p + 4^2 and p + 6^2 are also primes.at n=26A092475
- Primes p that remain prime through at least 2 iterations of the function f(p) = p^2 + 4.at n=32A116886
- Primes p that remain prime through at least 3 iterations of function f(p)=p^2+4.at n=2A116887
- Primes from binary expansion of Pi, another version. Starting with the first bit of the binary expansion, A004601 = 1,1,0,0,1,0,0,1,0,0,0,0,1,1,1,1,1,1,0,1,1,0,1,... we move rightward until we encounter another 1. Since 11 (= 3 in decimal) is prime, we move to the next 1 and repeat the process.at n=61A119017
- a(n+1) = gpf(2*prime(a(n-1)) + prime(a(n))) where gpf = greatest prime factor, with a(0)=1, a(1)=2.at n=37A122631
- Number of labeled PQ-trees with n leaves.at n=6A136629
- Primes of the form x^2 + 1848*y^2.at n=44A139668
- Primes congruent to 19 mod 47.at n=38A142370
- Primes congruent to 15 mod 53.at n=36A142545
- Primes congruent to 19 mod 59.at n=34A142746
- Primes congruent to 4 mod 61.at n=34A142802
- a(n) = A145818(2n-1).at n=37A145850