981
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 1430
- Proper Divisor Sum (Aliquot Sum)
- 449
- 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
- 648
- Möbius Function
- 0
- Radical
- 327
- Omega Function (Ω)
- 3
- 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
- 23
- Smith Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- neunhunderteinundachtzig· ordinal: neunhunderteinundachtzigste
- English
- nine hundred eighty-one· ordinal: nine hundred eighty-first
- Spanish
- novecientos ochenta y uno· ordinal: 981º
- French
- neuf cent quatre-vingt-un· ordinal: neuf cent quatre-vingt-unième
- Italian
- novecentoottantuno· ordinal: 981º
- Latin
- nongenti octoginta unus· ordinal: 981.
- Portuguese
- novecentos e oitenta e um· ordinal: 981º
Appears in sequences
- Number of monosubstituted alkanes C(n)H(2n+1)-X of the form shown in the Comments lines that are not stereoisomers.at n=16A000624
- Numbers that are a sum of distinct positive cubes in more than one way.at n=37A003998
- Number of entries in first n rows of Pascal's triangle not divisible by 3.at n=72A006048
- Crystal ball sequence for diamond.at n=10A007904
- Coordination sequence T1 for Zeolite Code CHA.at n=24A008066
- a(n) is the concatenation of n and 9n.at n=8A009474
- Pisot sequence E(9,15), a(n) = floor( a(n-1)^2/a(n-2) + 1/2 ).at n=9A014003
- Tetranacci numbers arising in connection with current algebras sp(2)_n.at n=9A014610
- Number of triples of different integers from [ 2,n ] with no global factor.at n=19A015618
- Positive integers n such that 2^n (mod n) == 2^9 (mod n).at n=51A015931
- Divisors of 981.at n=5A018757
- Cycle class sequence c(2n) (the number of true cycles of length 2n in which a certain node is included) for zeolite AWW = AlPO4-22 [Al24P24O96].2R starting with a T1 atom.at n=4A018992
- (n-2)-th Catalan number is congruent to 2n/3 mod n.at n=36A019468
- Numbers k such that the continued fraction for sqrt(k) has period 30.at n=6A020369
- First row of spectral array W(sqrt(3/2)).at n=8A022163
- Convolution of natural numbers with A023532.at n=48A023536
- Convolution of A000201 and A014306.at n=37A023666
- Discriminants of totally complex quartic fields.at n=32A023682
- a(n) = 1*t(n) + 2*t(n-1) + ... + k*t(n+1-k), where k=floor((n+1)/2) and t = A002808 (composite numbers).at n=17A023863
- a(n) = [ (3rd elementary symmetric function of P(n))/(first elementary symmetric function of P(n)) ], where P(n) = {first n+2 primes}.at n=6A024453