1861
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 16
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 1862
- Proper Divisor Sum (Aliquot Sum)
- 1
- 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
- 1860
- Möbius Function
- -1
- Radical
- 1861
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- 37
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 284
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Let A(n) = #{(i,j): i^2 + j^2 <= n}, V(n) = Pi*n, P(n) = A(n) - V(n); A000099 gives values of n where |P(n)| sets a new record; sequence gives A(A000099(n)).at n=18A000323
- Primes p of the form 3k+1 such that -sqrt(p) < sum_{x=1..p} cos(2*Pi*x^3/p) < sqrt(p).at n=42A000922
- 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=30A001844
- a(n) = n^2 written backwards.at n=40A002942
- Number of restricted solid partitions of n.at n=14A002974
- Primitive prime factors of the sequence k^2 + 1 (A002522) in the order that they are found.at n=42A005529
- Primes with both 10 and -10 as primitive root.at n=53A007349
- Primes whose reversal is a square.at n=5A007488
- Primes of form x^3 + y^3 + z^3 where x,y,z > 0.at n=43A007490
- Smallest prime > n^2.at n=42A007491
- Primes that divide at least one term of Sylvester's sequence s = A000058: s(n+1) = s(n)^2 - s(n) + 1, s(0) = 2.at n=13A007996
- Coordination sequence T3 for Zeolite Code DFO.at n=33A009877
- Coordination sequence for sigma-CrFe, Position Xa.at n=11A009962
- a(0) = 1, a(n) = 11*n^2 + 2 for n>0.at n=13A010003
- Primes p==1 (mod 6) such that 3 and -3 are both cubes (one implies other) modulo p.at n=43A014753
- Expansion of x/(1 - 6*x - 5*x^2).at n=5A015551
- Numbers k such that the continued fraction for sqrt(k) has period 21.at n=13A020360
- Primes that remain prime through 2 iterations of function f(x) = x + 6.at n=46A023241
- Primes that remain prime through 2 iterations of the function f(x) = 2x + 5.at n=28A023243
- Primes that remain prime through 2 iterations of function f(x) = 7x + 6.at n=24A023259