640
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 1530
- Proper Divisor Sum (Aliquot Sum)
- 890
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 256
- Möbius Function
- 0
- Radical
- 10
- Omega Function (Ω)
- 8
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 12
- 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
- yes
- Carmichael Number
- no
Classification
- Even
- yes
- Odd
- no
Names
- German
- sechshundertvierzig· ordinal: sechshundertvierzigste
- English
- six hundred forty· ordinal: six hundred fortieth
- Spanish
- seiscientos cuarenta· ordinal: 640º
- French
- six cent quarante· ordinal: six cent quarantième
- Italian
- seicentoquaranta· ordinal: 640º
- Latin
- sescenti quadraginta· ordinal: 640.
- Portuguese
- seiscentos e quarenta· ordinal: 640º
Appears in sequences
- Number of positive integers <= 2^n of the form 3*x^2 + 4*y^2.at n=12A000049
- Numbers that are the sum of 2 squares but not sum of 3 nonzero squares.at n=32A000549
- Expansion of 1/((1-x)^2*(1-x^2)*(1-x^3)).at n=25A000601
- Numbers k such that k / (sum of digits of k) is a square.at n=30A001102
- Numbers n such that every digit contains a loop (version 2).at n=55A001744
- a(n) = 10*4^n.at n=3A002066
- Number of divisors of n-th highly composite number.at n=52A002183
- Numbers k such that 25*4^k + 1 is prime.at n=18A002263
- Denominators of coefficients of log(1+x)/sqrt(1+x).at n=4A002550
- Coefficients for numerical differentiation.at n=2A002553
- a(n) = n*phi(n).at n=39A002618
- Number of 2-colored patterns on an n X n board.at n=7A002619
- Number of integer points in a certain quadrilateral scaled by a factor of n.at n=37A002789
- Number of rooted trees with n vertices in which vertices at the same level have the same degree.at n=35A003238
- Numbers that are the sum of 10 positive 6th powers.at n=10A003366
- Numbers that are the sum of 5 positive 7th powers.at n=5A003372
- Numbers of edges of regular polygons constructible with ruler (or, more precisely, an unmarked straightedge) and compass.at n=48A003401
- Numbers of the form 2^i*5^j with i, j >= 0.at n=26A003592
- Degrees of irreducible representations of group L3(9).at n=10A003899
- Degrees of irreducible representations of group L3(9).at n=9A003899