649
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 720
- Proper Divisor Sum (Aliquot Sum)
- 71
- 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
- 580
- Möbius Function
- 1
- Radical
- 649
- 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
- 144
- 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
- sechshundertneunundvierzig· ordinal: sechshundertneunundvierzigste
- English
- six hundred forty-nine· ordinal: six hundred forty-ninth
- Spanish
- seiscientos cuarenta y nueve· ordinal: 649º
- French
- six cent quarante-neuf· ordinal: six cent quarante-neufième
- Italian
- seicentoquarantanove· ordinal: 649º
- Latin
- sescenti quadraginta novem· ordinal: 649.
- Portuguese
- seiscentos e quarenta e nove· ordinal: 649º
Appears in sequences
- Numbers m such that Fibonacci(m) ends with m.at n=24A000350
- Flavius Josephus's sieve: Start with the natural numbers; at the k-th sieving step, remove every (k+1)-st term of the sequence remaining after the (k-1)-st sieving step; iterate.at n=28A000960
- Numbers n such that the sum of the squares of n consecutive positive odd numbers x^2 + (x+2)^2 + ... + (x+2n-2)^2 = k^2 for some integer k. The least values of x and k for each n are in A056131 and A056132, respectively.at n=41A001033
- Number of partitions of floor(5n/2) into n nonnegative integers each no more than 5.at n=16A001975
- Take solution to Pellian equation x^2 - n*y^2 = 1 with smallest positive y and x >= 0; sequence gives a(n) = x, or 1 if n is a square. A002349 gives values of y.at n=12A002350
- Take solution to Pellian equation x^2 - n*y^2 = 1 with smallest positive y and x >= 0; sequence gives a(n) = x, or 1 if n is a square. A002349 gives values of y.at n=51A002350
- Numbers that are the sum of 10 positive 5th powers.at n=26A003355
- Triangular numbers written backwards.at n=43A004158
- a(n) = least integer m > a(n-1) such that m - a(n-1) != a(j) - a(k) for all j, k less than n; a(1) = 1, a(2) = 2.at n=25A004978
- Number of permutations of (1,...,n) having n-7 inversions (n>=7).at n=4A005285
- Number of permutations of [n] with four inversions.at n=7A005287
- a(n) = cost of minimal multiplication-cost addition chain for n.at n=43A005766
- Solution to a Pellian equation: least x such that x^2 - n*y^2 = +- 1.at n=51A006702
- In the '3x+1' problem, these values for the starting value set new records for number of steps to reach 1.at n=17A006877
- Apocalyptic powers: 2^a(n) contains 666.at n=50A007356
- Coordination sequence T2 for Zeolite Code EUO.at n=16A008097
- Coordination sequence T2 for Zeolite Code SGT.at n=16A008230
- Coordination sequence T2 for Zeolite Code -CLO.at n=23A009851
- Apply partial sum operator twice to Stern's sequence.at n=9A014172
- a(n) = Sum_{k=1..n-1} ceiling(k^2/n).at n=43A014811