646
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 16
- Digital Root
- 7
- Palindromic Number
- yes
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 1080
- Proper Divisor Sum (Aliquot Sum)
- 434
- 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
- 288
- Möbius Function
- -1
- Radical
- 646
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- 100
- Smith Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- yes
- Odd
- no
Names
- German
- sechshundertsechsundvierzig· ordinal: sechshundertsechsundvierzigste
- English
- six hundred forty-six· ordinal: six hundred forty-sixth
- Spanish
- seiscientos cuarenta y seis· ordinal: 646º
- French
- six cent quarante-six· ordinal: six cent quarante-sixième
- Italian
- seicentoquarantasei· ordinal: 646º
- Latin
- sescenti quadraginta sex· ordinal: 646.
- Portuguese
- seiscentos e quarenta e seis· ordinal: 646º
Appears in sequences
- Number of monosubstituted alkanes C(n)H(2n+1)-X of the form shown in the Comments lines that are stereoisomers.at n=10A000623
- Triangle read by rows: T(n,k) = number of permutations of length n with exactly k rising or falling successions, for n >= 1, 0 <= k <= n-1.at n=21A001100
- Expansion of 1/((1-x)^2*(1-x^2)*(1-x^5)*(1-x^10)*(1-x^20)).at n=26A001305
- Number of ways of making change for n cents using coins of 1, 2, 4, 10, 20, 40, 100 cents.at n=52A001310
- Number of ways of making change for n cents using coins of 1, 2, 4, 10, 20, 40, 100 cents.at n=53A001310
- Numbers n such that every digit contains a loop (version 2).at n=57A001744
- Numbers dividing A002037(i) and larger than A002037(i-1), for some i>0.at n=53A002038
- Hertzsprung's problem: ways to arrange n non-attacking kings on an n X n board, with 1 in each row and column. Also number of permutations of length n without rising or falling successions.at n=7A002464
- Number of unlabeled connected planar simple graphs with n nodes.at n=7A003094
- Numbers that are the sum of 7 positive 5th powers.at n=20A003352
- Numbers that are the sum of 11 positive 7th powers.at n=5A003378
- Degrees of irreducible representations of Janko group J3.at n=6A003906
- Degrees of irreducible representations of Janko group J3.at n=7A003906
- Expansion of (1 + x - x^5) / (1 - x)^3.at n=31A004120
- a(n) = floor(Fibonacci(n)/4).at n=18A004697
- Numbers that are the sum of at most 11 positive 7th powers.at n=56A004873
- a(n) = round(n*phi^6), where phi is the golden ratio, A001622.at n=36A004941
- a(n) = ceiling(n*phi^6), where phi is the golden ratio.at n=36A004961
- Number of alternating sign 2n+1 X 2n+1 matrices symmetric about the vertical axis (VSASM's); also 2n X 2n off-diagonally symmetric alternating sign matrices (OSASM's).at n=4A005156
- Number of binary phylogenetic trees with n labels.at n=4A006681