1851
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2472
- Proper Divisor Sum (Aliquot Sum)
- 621
- 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
- 1232
- Möbius Function
- 1
- Radical
- 1851
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 130
- 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
- Let A(n) = #{(i,j,k): i^2 + j^2 + k^2 <= n}, V(n) = (4/3)Pi*n^(3/2), P(n) = A(n) - V(n); A000092 gives values of n where |P(n)| sets a new record; sequence gives (nearest integer to, I believe) P(A000092(n)).at n=40A000223
- One half of number of non-self-conjugate partitions; also half of number of asymmetric Ferrers graphs with n nodes.at n=28A000701
- Number of protruded partitions of n with largest part at most 6.at n=11A005407
- Sum of the first n primes.at n=32A007504
- a(n) = n OR n^2 (applied to binary expansions).at n=42A007745
- Coordination sequence T6 for Zeolite Code DDR.at n=27A008076
- a(0) = 1, a(n) = n^2 + 2 for n > 0.at n=43A010000
- Least d such that period of continued fraction for sqrt(d) contains n (n^2+2 if n odd, (n/2)^2+1 if n even).at n=42A013945
- Fibonacci sequence beginning 3, 11.at n=12A022123
- a(n) = [ (2nd elementary symmetric function of P(n))/(first elementary symmetric function of P(n)) ], where P(n) = {first n+1 primes}.at n=42A024452
- Index of 10^n within the sequence of the numbers of the form 5^i*10^j.at n=50A025743
- a(n) = T(n,n-2), where T is the array in A026386.at n=40A026393
- a(n) = T(n,0) + T(n,1) + ... + T(n,[ n/2 ]), T given by A026907.at n=6A026916
- Number of partitions of n into an odd number of parts.at n=28A027193
- [ exp(17/18)*n! ].at n=5A030878
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 43.at n=0A031541
- Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 43.at n=0A031721
- "EFK" (unordered, size, unlabeled) transform of 2,1,1,1,...at n=41A032303
- Floor( 7*n^2/2 ).at n=23A032525
- Coordination sequence T2 for Zeolite Code SBS.at n=34A033609