15555
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
- 16
- Divisor Sum
- 26784
- Proper Divisor Sum (Aliquot Sum)
- 11229
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7680
- Möbius Function
- 1
- Radical
- 15555
- 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
- no
- Perfect Square
- no
- Perfect Cube
- no
- Pentagonal Number
- yes
- 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
- 84
- 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) = (n+1)*(5*n^2+4*n+1).at n=14A027849
- Numbers in which all pairs of consecutive base-8 digits differ by 3.at n=52A033079
- Numbers whose maximal base-10 run length is 4.at n=22A033285
- Numbers having four 0's in base 6.at n=32A043372
- Numbers having four 5's in base 10.at n=1A043512
- Numbers whose base-4 representation contains exactly three 0's and four 3's.at n=13A045080
- a(n) = a(n-1) + 2*a(floor(n/2)) if n > 0, otherwise 1.at n=29A058039
- List of codewords in binary lexicode with Hamming distance 8 written as decimal numbers.at n=7A075940
- Expansion of g.f. (1+4*x)/((1-x)*(1-10*x)).at n=4A099915
- Pentagonal numbers (A000326) whose digit reversal is a semiprime (A001358).at n=29A115709
- Pentagonal numbers divisible by 5.at n=41A117793
- Pentagonal numbers with only odd digits.at n=14A117985
- Primitive elements of A119432.at n=34A119433
- Pentagonal numbers (A000326) which are the sum of 2 other positive pentagonal numbers.at n=22A136117
- Least number k such that k*p(n)*(k*p(n)+1)-1, k*p(n)*(k*p(n)+1)+1, k*p(n)*(k*p(n)+3)-1 and k*p(n)*(k*p(n)+3)+1 are all primes, two pairs of twin primes, with p(i) = i-th prime.at n=13A139638
- Partial sums of A000048.at n=18A173278
- Row sums of triangle A182701.at n=16A182705
- Number of (n+1) X 3 0..2 arrays with all 2 X 2 subblock sums the same.at n=6A183996
- Number of (n+1) X 8 0..2 arrays with all 2 X 2 subblock sums the same.at n=1A184001
- T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with all 2X2 subblock sums the same.at n=29A184003