666
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- yes
- Repdigit
- yes
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 12
- Divisor Sum
- 1482
- Proper Divisor Sum (Aliquot Sum)
- 816
- 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
- 216
- Möbius Function
- 0
- Radical
- 222
- Omega Function (Ω)
- 4
- 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
- yes
- 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
- 113
- Smith Number
- yes
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
- no
- Carmichael Number
- no
Classification
- Even
- yes
- Odd
- no
Names
- German
- sechshundertsechsundsechzig· ordinal: sechshundertsechsundsechzigste
- English
- six hundred sixty-six· ordinal: six hundred sixty-sixth
- Spanish
- seiscientos sesenta y seis· ordinal: 666º
- French
- six cent soixante-six· ordinal: six cent soixante-sixième
- Italian
- seicentosessantasei· ordinal: 666º
- Latin
- sescenti sexaginta sex· ordinal: 666.
- Portuguese
- seiscentos e sessenta e seis· ordinal: 666º
Appears in sequences
- Let A(n) = #{(i,j,k): i^2 + j^2 + k^2 <= n}, V(n) = (4/3)Pi*n^(3/2), P(n) = A(n) - V(n); sequence gives values of n where |P(n)| sets a new record.at n=22A000092
- Number of switching networks (see Harrison reference for precise definition).at n=1A000815
- Numbers in which every digit contains at least one loop (version 1).at n=21A001743
- Related to Zarankiewicz's problem.at n=34A001841
- a(n) = 6*(10^n - 1)/9.at n=3A002280
- Numbers k such that (k^2 + k + 1)/13 is prime.at n=32A002642
- Doubly triangular numbers: a(n) = n*(n+1)*(n^2+n+2)/8.at n=8A002817
- Numbers k such that 2*25^k - 1 is prime.at n=9A002958
- Palindromic triangular numbers.at n=8A003098
- High temperature series for spherical model susceptibility on 3-dimensional simple cubic lattice.at n=4A003279
- Number of 2-factors in C_5 X P_n.at n=3A003730
- Triangular numbers written backwards.at n=36A004158
- a(n) = ceiling(exp((n-1)/2)).at n=14A005181
- Record values in A005210.at n=29A005211
- Triangular numbers together with squares (excluding 0).at n=58A005214
- P-positions in Epstein's Put or Take a Square game.at n=23A005240
- Number of weighted voting procedures.at n=9A005256
- Number of partitions of [n] where the first k elements are marked (0 <= k <= n-1) and at least k blocks contain their own index.at n=5A005490
- Number of ways of placing n non-attacking bishops on an n X n board so that every square is attacked (or occupied).at n=8A005635
- Numbers whose ternary expansion contains no 1's.at n=52A005823