15825
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
- 12
- Divisor Sum
- 26288
- Proper Divisor Sum (Aliquot Sum)
- 10463
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8400
- Möbius Function
- 0
- Radical
- 3165
- Omega Function (Ω)
- 4
- 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
- 146
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- Numbers k that divide s(k), where s(1)=1, s(j)=21*s(j-1)+j.at n=36A014872
- Numerators of continued fraction convergents to sqrt(255).at n=4A041478
- Column 3 of A052250.at n=11A052251
- Number of parallelogram polyominoes of site-perimeter n (also called staircase polyominoes, although that term is overused).at n=17A075125
- Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 3,3,0,2,2 for x=0,1,2,3,4.at n=4A197451
- Number of nX5 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 3,3,0,2,2 for x=0,1,2,3,4.at n=4A197454
- T(n,k)=Number of nXk 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 3,3,0,2,2 for x=0,1,2,3,4.at n=40A197457
- Size of the equivalence class of S_n containing the identity permutation under transformations of positionally adjacent elements of the form abc <--> acb <--> cba where a<b<c.at n=8A212418
- Numbers k such that k!4 + 2^2 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662).at n=35A291122
- Number of n X 2 0..1 arrays with each 1 horizontally or vertically adjacent to 1 or 3 1s.at n=11A295091
- Number of partitions of n in which the sequence of the sum of the same summands is nondecreasing.at n=47A304405