381
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 12
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 512
- Proper Divisor Sum (Aliquot Sum)
- 131
- 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
- 252
- Möbius Function
- 1
- Radical
- 381
- 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
- 107
- Smith 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
Names
- German
- dreihunderteinundachtzig· ordinal: dreihunderteinundachtzigste
- English
- three hundred eighty-one· ordinal: three hundred eighty-first
- Spanish
- trescientos ochenta y uno· ordinal: 381º
- French
- trois cent quatre-vingt-un· ordinal: trois cent quatre-vingt-unième
- Italian
- trecentoottantuno· ordinal: 381º
- Latin
- trecenti octoginta unus· ordinal: 381.
- Portuguese
- trezentos e oitenta e um· ordinal: 381º
Appears in sequences
- a(n) = least m such that if a/b < c/d where a,b,c,d are integers in [0,n], then a/b < k/m < c/d for some integer k.at n=23A001000
- Number of sublattices of index n in generic 3-dimensional lattice.at n=18A001001
- Maximal number of unattacked squares with n queens on n X n board (answers for n >= 17 only probable).at n=28A001366
- Number of permutations of length n with longest increasing subsequence of length 3.at n=3A001454
- Nearest integer to 2*n*log(n).at n=49A001618
- a(n) = 3 * prime(n).at n=30A001748
- Central polygonal numbers: a(n) = n^2 - n + 1.at n=20A002061
- Numbers k for which the rank of the elliptic curve y^2 = x^3 + k is 2.at n=58A002155
- Losing initial positions in game: two players alternate in removing >= 1 stones; last player wins; first player may not remove all stones; each move <= 3 times previous move.at n=17A003411
- Divisors of 2^14 - 1.at n=5A003525
- Divisors of 2^28 - 1.at n=13A003536
- Divisors of 2^42 - 1.at n=13A003547
- Inconsummate numbers in base 10: no number is this multiple of the sum of its digits (in base 10).at n=18A003635
- a(n) = round(100*log_2(n)).at n=13A004263
- a(n) = ceiling(100*log_2(n)).at n=13A004264
- Expansion of x*(1+x^2+x^4)/((1-x)*(1-x^2)*(1-x^3)).at n=39A004652
- Numbers of the form 8k+5; or, numbers whose binary expansion ends in 101.at n=47A004770
- a(n) = ceiling(n*phi^9), where phi is the golden ratio, A001622.at n=5A004964
- Central pentanomial coefficients: largest coefficient of (1 + x + ... + x^4)^n.at n=5A005191
- a(n) = Sum_t t*F(n,t), where F(n,t) (see A095133) is the number of forests with n (unlabeled) nodes and exactly t trees.at n=8A005196