1985
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 23
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2388
- Proper Divisor Sum (Aliquot Sum)
- 403
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 1584
- Möbius Function
- 1
- Radical
- 1985
- 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
- 50
- 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
- Centered square numbers: a(n) = 2*n*(n+1)+1. Sums of two consecutive squares. Also, consider all Pythagorean triples (X, Y, Z=Y+1) ordered by increasing Z; then sequence gives Z values.at n=31A001844
- Expansion of (1-x)/(1 - 3*x + x^2)^2.at n=6A001870
- Divisors of 2^44 - 1.at n=15A003549
- Odd numbers not of form p + 2^k (de Polignac numbers).at n=46A006285
- Coordination sequence T1 for Zeolite Code HEU.at n=29A008116
- Coordination sequence T2 for Zeolite Code RTH.at n=31A009894
- a(n) = floor( n*(n-1)*(n-2)*(n-3)/22 ).at n=16A011932
- exp(arctan(x)+arcsin(x))=1+2*x+4/2!*x^2+7/3!*x^3+8/4!*x^4+25/5!*x^5...at n=7A012985
- sinh(arctan(x)+arcsin(x))=2*x+7/3!*x^3+25/5!*x^5+1985/7!*x^7...at n=3A012990
- Integers that are squarefree and also the sum of first k squarefrees for some k.at n=29A013932
- Pseudoprimes to base 63.at n=9A020191
- Strong pseudoprimes to base 63.at n=4A020289
- Numbers k such that the continued fraction for sqrt(k) has period 19.at n=14A020358
- Numbers k such that Fibonacci(k) == -5 (mod k).at n=52A023165
- a(n) = 1*t(n) + 2*t(n-1) + ... + k*t(n+1-k), where k=floor((n+1)/2) and t = A008578 ({1} U primes).at n=18A023862
- [ (4th elementary symmetric function of S(n))/(2nd elementary symmetric of S(n)) ], where S(n) = {3,4, ..., n+5}.at n=13A024194
- a(n) = s(1)*s(n) + s(2)*s(n-1) + ... + s(k)*s(n+1-k), where k = floor((n+1)/2), s = (Fibonacci numbers).at n=13A024458
- a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n-k+1), where k = [ n/2 ] and s = (Fibonacci numbers).at n=12A025078
- Numbers that are the sum of 3 distinct nonzero squares in exactly 9 ways.at n=33A025347
- a(n) = n^2 + n + 5.at n=44A027690