205
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 7
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 252
- Proper Divisor Sum (Aliquot Sum)
- 47
- 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
- 160
- Möbius Function
- 1
- Radical
- 205
- 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
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 26
- 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
- zweihundertfünf· ordinal: zweihundertfünfste
- English
- two hundred five· ordinal: two hundred fifth
- Spanish
- doscientos cinco· ordinal: 205º
- French
- deux cent cinq· ordinal: deux cent cinqième
- Italian
- duecentocinque· ordinal: 205º
- Latin
- ducenti quinque· ordinal: 205.
- Portuguese
- duzentos e cinco· ordinal: 205º
Appears in sequences
- Number of ways of making change for n cents using coins of 1, 2, 5, 10 cents.at n=41A000008
- Number of positive integers <= 2^n of form x^2 + 2 y^2.at n=9A000067
- Let A(n) = #{(i,j): i^2 + j^2 <= n}, V(n) = Pi*n, P(n) = A(n) - V(n); sequence gives values of n where |P(n)| sets a new record.at n=11A000099
- Denumerants: Expansion of 1/((1-x)*(1-x^2)*(1-x^5)).at n=60A000115
- Number of nonnegative solutions to x^2 + y^2 + z^2 <= n.at n=42A000606
- Erroneous version of A007535.at n=41A000783
- Genus of complete graph on n nodes.at n=52A000933
- Lucky numbers.at n=40A000959
- Number of ways of making change for n cents using coins of 1, 2, 5, 10, 50, 100 cents.at n=41A001312
- Primes multiplied by 5.at n=12A001750
- a(n) = floor((n+2/3)*(5+sqrt(13))/2); v-pile positions in the 3-Wythoff game.at n=47A001960
- v-pile positions of the 4-Wythoff game with i=1.at n=39A001964
- Numbers of the form (p^2 - 49)/120 where p is prime.at n=17A002382
- Multiples of Euler numbers.at n=2A002438
- a(n) = 7^n - 3*4^n + 2*3^n.at n=2A002501
- Earliest sequence with a(a(n))=5n.at n=42A002518
- a(n) = 2*a(n-1) + 9*a(n-2), with a(0) = 0, a(1) = 1.at n=5A002534
- a(n) = Sum_{k=1..n-1} floor((n-k)/k).at n=61A002541
- Numbers k such that (k^2 + k + 1)/21 is prime.at n=12A002644
- Numbers k such that (k^2 + 1)/2 is prime.at n=36A002731