15721
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 16
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 16000
- Proper Divisor Sum (Aliquot Sum)
- 279
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 15444
- Möbius Function
- 1
- Radical
- 15721
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
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
- 84
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- 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
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 70 ones.at n=27A031838
- Number of partitions of n into parts 3k and 3k+1 with at least one part of each type.at n=51A035618
- Numerators of continued fraction convergents to sqrt(673).at n=5A042294
- Smallest a(n)>2 such that all integers strictly between a(n)-n and a(n) are composite.at n=37A075741
- Number of partitions of n such that the number of different parts is odd.at n=38A090794
- Diagonal sums of A110135 when read as a number triangle.at n=8A110137
- a(n) = 10*n^2 - 7*n + 1.at n=40A158186
- First string of 43 consecutive composite numbers.at n=37A177949
- a(n) = floor(1/{(10+n^4)^(1/4)}), where {}=fractional part.at n=33A184634
- Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x>2*y*z.at n=15A211797
- Number of 2 X n arrays of the minimum value of corresponding elements and their horizontal, diagonal or antidiagonal neighbors in a random, but sorted with lexicographically nondecreasing rows and columns, 0..2 2 X n array.at n=25A219382
- Expansion of Product_{k>=1} (1 + x^(3*k-1))^(3*k-1).at n=36A262948
- Where record values occur in A276781, when starting from A276781(2)=1.at n=38A276782
- Numbers k such that k!6 + 18 is prime, where k!6 is the sextuple factorial number (A085158 ).at n=32A288445
- a(n) is the smallest integer k > n such that (k+1)(k+2)...(2k-2n+1)/(k(k-1)...(k-n+1)) is an integer.at n=37A290791
- Number of integer partitions of n with frequency depth floor(sqrt(n)).at n=39A325252
- Number of integer partitions of n with the maximum adjusted frequency depth for partitions of n.at n=39A325254
- Number of integer partitions of n with frequency depth round(sqrt(n)).at n=39A325271
- Expansion of Product_{k>=1} (1 + x^k * (1 + k*x)).at n=21A336980
- a(n) = greatest number in row n of the array in A225485.at n=38A364810