9919
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 28
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 12320
- Proper Divisor Sum (Aliquot Sum)
- 2401
- 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
- 7776
- Möbius Function
- -1
- Radical
- 9919
- 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
- 148
- 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
- a(n) is the solution to the postage stamp problem with 4 denominations and n stamps.at n=27A001209
- Centered octahedral numbers (crystal ball sequence for cubic lattice).at n=19A001845
- Expansion of (1+x)(1+x^2)/(1-x-x^3).at n=23A003410
- a(n) = C(n,1) + C(n,2) + C(n,3), or n*(n^2 + 5)/6.at n=39A004006
- Differences between two positive cubes in exactly 2 ways.at n=8A014440
- Pseudoprimes to base 38.at n=45A020166
- Pseudoprimes to base 66.at n=29A020194
- Strong pseudoprimes to base 16.at n=36A020242
- Strong pseudoprimes to base 82.at n=20A020308
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 21 ones.at n=2A031789
- Difference between two positive cubes in more than one way.at n=9A034179
- Numbers ending with '9' that are the difference of two positive cubes.at n=32A038864
- Denominators of continued fraction convergents to sqrt(759).at n=9A042463
- Numbers having three 9's in base 10.at n=19A043527
- A Diaconis-Mosteller approximation to the Birthday problem function.at n=43A050255
- Numbers that are the sum of two (possibly negative) cubes in at least 2 ways.at n=32A051347
- Expansion of (1 - x^2)/(1 - x - x^3).at n=27A058278
- Number of 3 X 3 matrices, with elements from {0,...,n}, having the property that the middle element of each of the eight 3-element horizontal, vertical and diagonal lines equals the average of the two end elements.at n=38A059329
- a(1) = 16; for n > 1, a(n) is the smallest integer > 0 such that the concatenation a(n)a(n-1)...a(2)a(1) is a square.at n=3A065778
- Sum of diagonal elements and those below it for a square matrix of integers, starting with 1.at n=12A066804