12561
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 17280
- Proper Divisor Sum (Aliquot Sum)
- 4719
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8112
- Möbius Function
- -1
- Radical
- 12561
- Omega Function (Ω)
- 3
- 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
- yes
- 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
- 37
- 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
- Cubes written in base 7.at n=14A004637
- Numbers k such that sigma(k) = sigma(k+4).at n=17A015863
- Numbers k such that sigma(k) = sigma(k+6).at n=31A015866
- Numbers whose set of base-16 digits is {1,3}.at n=22A032923
- a(n) = (2*n-1)*(4*n-1).at n=40A033567
- Let R(i,j) be the rectangle with antidiagonals 1; 2,3; 4,5,6; ...; each k is an R(i(k),j(k)) and A057041(n)=j(F(n)), where F(n) is the n-th Fibonacci number.at n=40A057041
- Triangular numbers with sum of digits = 15.at n=24A068130
- Triangular numbers with property that digits alternate in parity.at n=27A068882
- Triangular numbers with property that swapping first and last digits also gives a triangular number.at n=33A069708
- a(n) = (25*n^2 - 15*n + 2)/2.at n=32A080857
- Divisors of 10^13 - 1.at n=10A109933
- Triangular numbers for which the sum of the digits is a hexagonal number.at n=34A117309
- Triangular numbers that are products of three distinct primes.at n=38A128896
- Triangular numbers which are the average of two consecutive primes.at n=35A130178
- Row sums of triangle A131819.at n=32A131820
- a(n) = 3*a(n-1)+n if a(n-1) is not divisible by 2, or a(n) = a(n-1)/2 otherwise.at n=70A135294
- G.f. satisfies: A(x) = 1 + x*A(x)^2/A(-x).at n=9A143339
- Triangular numbers n*(n+1)/2 with n and n+1 composite, where number of prime factors in n = number of prime factors in n+1. (Prime factors are counted with multiplicity.)at n=28A144486
- Triangular numbers generated in A224218. That is, the triangular numbers generated by the operation triangular(i) XOR triangular(i+1) along increasing i.at n=42A220689
- Triangular numbers generated in A224218. That is, the triangular numbers generated by the operation triangular(i) XOR triangular(i+1) along increasing i.at n=43A220689