391
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 432
- Proper Divisor Sum (Aliquot Sum)
- 41
- 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
- 352
- Möbius Function
- 1
- Radical
- 391
- 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
- 120
- Smith Number
- yes
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
- dreihunderteinundneunzig· ordinal: dreihunderteinundneunzigste
- English
- three hundred ninety-one· ordinal: three hundred ninety-first
- Spanish
- trescientos noventa y uno· ordinal: 391º
- French
- trois cent quatre-vingt-onze· ordinal: trois cent quatre-vingt-onzième
- Italian
- trecentonovantuno· ordinal: 391º
- Latin
- trecenti nonaginta unus· ordinal: 391.
- Portuguese
- trezentos e noventa e um· ordinal: 391º
Appears in sequences
- Number of partitions of n into at most 6 parts.at n=22A001402
- a(n) = (8*n+1)*(8*n+7).at n=2A001533
- Nearest integer to 2*n*log(n).at n=50A001618
- Numbers dividing A002037(i) and larger than A002037(i-1), for some i>0.at n=35A002038
- a(n) = Fibonacci(n) + n.at n=14A002062
- Numbers k for which the rank of the elliptic curve y^2 = x^3 - k is 2.at n=52A002154
- Numbers m such that 3*2^m - 1 is prime.at n=22A002235
- Numbers y such that p^2 = x^2 + y^2, 0 < x < y, p = A002144(n).at n=38A002365
- Odd squarefree numbers with an even number of prime factors that have no prime factors greater than 31.at n=36A002557
- Numbers k such that (k^2 + 1)/2 is prime.at n=59A002731
- Coefficients in expansion of permanent of infinite tridiagonal matrix shown below.at n=36A003113
- The number of superpositions of cycles of order n of the groups E_3 and D_n.at n=3A003224
- Numbers that are the sum of 11 positive 4th powers.at n=47A003345
- Numbers that are the sum of 10 positive 7th powers.at n=3A003377
- Odd numbers that are not of the form x^2 + y^2 + 10*z^2.at n=15A003585
- a(n) = n^3 + n^2 - 1.at n=6A003777
- Primes written backwards.at n=43A004087
- Number of partitions of n of the form a_1*b_1^2 + a_2*b_2^2 + ...; number of semisimple rings with p^n elements for any prime p.at n=16A004101
- a(n) = round(100*log_2(n)).at n=14A004263
- a(n) = ceiling(100*log_2(n)).at n=14A004264