13861
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 14112
- Proper Divisor Sum (Aliquot Sum)
- 251
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 13612
- Möbius Function
- 1
- Radical
- 13861
- 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
- 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
- 151
- 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(n) = p*(p-1)/2 for p = prime(n).at n=38A008837
- Numbers k such that the continued fraction for sqrt(k) has period 90.at n=32A020429
- a(n) = (2*n-1)*(4*n-1).at n=42A033567
- Maximum cardinality of finite D0L sequence over an alphabet with n symbols.at n=37A039952
- Expansion of (2-3*x-x^2)/((1-x)*(1-2*x-x^2)).at n=11A052937
- Smallest number that is centered polygonal in exactly n ways.at n=16A063773
- Triangular numbers whose reverse is prime.at n=11A066751
- Triangular numbers which are a concatenation of two or more positive triangular numbers.at n=26A068144
- Triangular numbers which are the product of two primes.at n=15A068443
- Centered 14-gonal numbers.at n=44A069127
- Centered 22-gonal numbers.at n=35A069173
- Triangular numbers with property that swapping first and last digits also gives a triangular number.at n=35A069708
- Numbers k such that gcd(3k,8^k+1) = 3 but k does not divide the numerator of B(2k) (the Bernoulli numbers).at n=20A070193
- Third row of Pascal-(1,6,1) array A081581.at n=24A081591
- Smallest triangular number which is one more than the product of n distinct numbers > 1.at n=5A081951
- Sort the digits of these triangular numbers into descending order and drop zeros to get primes.at n=21A082923
- Triangular numbers which are one more than a product of distinct triangular numbers.at n=12A083517
- Triangular numbers whose sum of aliquot divisors is a prime number.at n=13A083676
- a(n) = smallest k where (10^k+1)=0 mod prime(n)^2, or 0 if no such k exists.at n=38A086981
- Expansion of g.f. (1+8*x-x^2)/((1+x)*(1-6*x+x^2)).at n=5A105058