15311
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 11
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 15624
- Proper Divisor Sum (Aliquot Sum)
- 313
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 15000
- Möbius Function
- 1
- Radical
- 15311
- 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
- a(0) = 1, a(n) = 21*n^2 + 2 for n>0.at n=27A010011
- Pseudoprimes to base 20.at n=40A020148
- Strong pseudoprimes to base 20.at n=9A020246
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 31 ones.at n=2A031799
- Molien series for group G_{1,2}^{8} of order 1536.at n=32A051462
- Sum of the primes in ordered 3 X 3 prime squares.at n=29A105089
- Numerators of the triangle of coefficients T(n,k), read by rows, that satisfy: y^x = Sum_{n=0..x} R_n(y)*x^n for all nonnegative integers x, y, where R_n(y) = Sum_{k=0..n} T(n,k)*y^k and T(n,k) = a(n,k)/A107046(n,k).at n=21A107045
- Irregular triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k white corners.at n=32A140711
- a(n) = (prime(n) - 1)*(prime(n+1) - 1)/2 + 3.at n=39A201498
- G.f.: (-1+6*x)/(1-3*x-2*x^2).at n=8A246313
- a(n) = (1 + Sum_{j=0..n} (C(n,j)*C(3*j-1,j))) / 2.at n=6A254747
- Triangle of order m: C(n,k) = k*(n-k+1)^(k+m)+n-k, 0 <= k <= n, m = 0, read by rows.at n=52A278910