643
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
- 2
- Divisor Sum
- 644
- 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
- 642
- Möbius Function
- -1
- Radical
- 643
- 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
- 25
- Smith Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 117
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Names
- German
- sechshundertdreiundvierzig· ordinal: sechshundertdreiundvierzigste
- English
- six hundred forty-three· ordinal: six hundred forty-third
- Spanish
- seiscientos cuarenta y tres· ordinal: 643º
- French
- six cent quarante-trois· ordinal: six cent quarante-troisième
- Italian
- seicentoquarantatre· ordinal: 643º
- Latin
- sescenti quadraginta tres· ordinal: 643.
- Portuguese
- seiscentos e quarenta e três· ordinal: 643º
Appears in sequences
- Primes that divide at least one term in every Fibonacci sequence.at n=25A000057
- Primes p of the form 3k+1 such that Sum_{x=1..p} cos(2*Pi*x^3/p) > sqrt(p).at n=26A000921
- Twin primes.at n=56A001097
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/3.at n=8A001133
- Prime determinants of forms with class number 2.at n=54A002052
- a(n) is the smallest prime p such that each of the first n primes has three cube roots mod p.at n=2A002225
- Number of permutations of length n without 3-sequences.at n=6A002628
- Number of precomplete Post functions of n variables.at n=4A002826
- Numbers that are the sum of 4 nonzero 4th powers.at n=30A003338
- Numbers that are the sum of 8 positive 7th powers.at n=5A003375
- Divisible only by primes congruent to 6 mod 7.at n=21A004624
- Numbers that are the sum of at most 4 nonzero 4th powers.at n=69A004833
- Numbers that are the sum of at most 8 positive 7th powers.at n=38A004870
- Numbers that are the sum of at most 9 positive 7th powers.at n=43A004871
- Numbers that are the sum of at most 10 positive 7th powers.at n=48A004872
- Numbers that are the sum of at most 11 positive 7th powers.at n=53A004873
- a(n) = floor(n*phi^12), where phi is the golden ratio, A001622.at n=2A004927
- Class 4- primes (for definition see A005109).at n=11A005112
- Fortunate numbers: least m > 1 such that m + prime(n)# is prime, where p# denotes the product of all primes <= p.at n=32A005235
- Discriminants of imaginary quadratic fields with class number 3 (negated).at n=13A006203