16653
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
- 2
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 27776
- Proper Divisor Sum (Aliquot Sum)
- 11123
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8640
- Möbius Function
- 1
- Radical
- 16653
- Omega Function (Ω)
- 4
- Little Omega Function (ω)
- 4
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- yes
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 66
- Smith Number
- yes
- 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
- Quasi-Carmichael numbers to base -7: squarefree composites n such that prime p|n ==> p+7|n+7.at n=8A029567
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 86.at n=27A031584
- f(n,n+3) where f is given in A034261.at n=6A034270
- Numerators of continued fraction convergents to sqrt(991).at n=4A042918
- a(n) = 25*n*(n + 1)/2 + 3.at n=36A061793
- Triangular numbers with sum of digits = 21.at n=13A068131
- Triangular numbers of the form 21*k.at n=34A069499
- Smaller of the two successive triangular numbers which differ in the use of only one digit.at n=32A077759
- Smith triangular numbers.at n=7A098840
- Structured rhombic triacontahedral numbers (vertex structure 11).at n=12A100164
- Row sums of triangle A101224, which is related to the Flavius sieve (A000960).at n=26A101105
- Concatenation of triangular number k and its 10's complement is prime.at n=12A108970
- a(n) = n*(n+1)*(n^2+n+1)/2.at n=13A110450
- Triangular numbers for which the sum of the digits is an octagonal number.at n=16A117523
- Triangular numbers n*(n+1)/2 with n and n+1 composite, where number of prime factors in n > number of prime factors in n+1.at n=33A144523
- a(n) = (prime(n))^2 - (nonprime(n))^2.at n=32A161757
- Number of reduced words of length n in the Weyl group B_13.at n=6A161859
- Number of reduced words of length n in the Weyl group D_13.at n=6A162300
- a(n) = A185128(n) + A185129(n).at n=7A185243
- First differences of A036449, triangular numbers by definition.at n=6A189475