15545
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 18660
- Proper Divisor Sum (Aliquot Sum)
- 3115
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 12432
- Möbius Function
- 1
- Radical
- 15545
- 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
- 115
- 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 whose decimal representation, read as a base-20 value and divided by k, yields an integer.at n=47A032571
- n*10^4-1, n*10^4-3, n*10^4-7 and n*10^4-9 are all prime.at n=3A064978
- Triangle read by rows: T(n,k) = the number of Dyck paths of semilength n with k UDDU's.at n=33A135306
- (n^3 - n + 15)/3.at n=35A155757
- Coefficient of x^2 in the reduction of the n-th Fibonacci polynomial by x^3->x^2+x+1. See Comments.at n=14A192651
- Constant term of the reduction by x^2->x+1 of the polynomial p(n,x) defined below in Comments.at n=18A192757
- Beastly reciprocals, or numbers k such that digitsum(1/k) = 666.at n=32A244661
- Numbers n such that n!3 - 3^3 is prime, where n!3 = n!!! is a triple factorial number (A007661).at n=25A247463
- Numbers n such that 36n+11, 36(n+1)+11, 36(n+2)+11 and 36(n+3)+11 are prime.at n=19A255608
- Numbers n such that 17^n is the highest power of 17 dividing A240751(n).at n=3A286008
- The smallest positive integer whose greedy representation as a sum of 3-smooth numbers (A003586) requires n terms.at n=5A296840
- a(n) = 1^2 - 3^4 + 5^6 - 7^8 + 9^10 - 11^12 + 13^14 - ... + (up to n).at n=5A319438
- Partial sums of A323183.at n=42A323187
- a(0) = 1; a(n) = (1/n) * Sum_{k=1..n} binomial(n,k)^2 * k^3 * a(n-k).at n=5A337591
- Number of partitions of n into 7 or more parts.at n=29A347543
- Triangle read by rows: T(n,k) is the number of unsensed combinatorial maps with n edges and k vertices, 1 <= k <= n + 1.at n=31A380616
- G.f.: Sum_{k>=0} x^k * Product_{j=1..6*k} (1 + x^j).at n=48A385070