16491
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
- 23040
- Proper Divisor Sum (Aliquot Sum)
- 6549
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10472
- Möbius Function
- -1
- Radical
- 16491
- 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
- 66
- 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
- Fibonacci sequence beginning 6, 13.at n=16A022388
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (odd natural numbers), t = (primes).at n=29A024603
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (odd natural numbers), t = (primes).at n=28A025117
- a(n) = T(n, 2*n-5), T given by A027926.at n=17A027928
- Odd 9-gonal (or enneagonal) numbers.at n=34A028991
- a(n) = (2*n+1)*(7*n+1).at n=34A033572
- a(n) = T(n,n-5), array T as in A055801.at n=36A055805
- Numbers k such that k!! + 2^9 is prime.at n=13A076196
- Number of (w,x,y,z) with all terms in {1,...,n} and w + x > 2y + 2z.at n=19A212564
- (8*n^3 + 3*n^2 + n) / 6.at n=22A219054
- Number of idempotent 3X3 -n..n matrices of rank 2.at n=10A223452
- a(n) = n-th pi-based antiderivative of 7.at n=20A259168
- Numbers k such that (14*10^k + 211)/9 is prime.at n=15A294941
- Positive integers that have exactly ten representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.at n=5A317400
- a(n) = Sum_{k=0..floor(n/2)} binomial(4*n-k,n-2*k).at n=5A371743
- G.f. satisfies A(x) = Sum_{n>=1} 2^(n-1) * A(x^(2*n))/A(x^n), with A(0) = 0 and A'(0) = 1.at n=14A378262