55
domain: N
Properties
Digital Properties
- Digit Count
- 2
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- yes
- Repdigit
- yes
- Automorphic
- no
- Kaprekar Number
- yes
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 72
- Proper Divisor Sum (Aliquot Sum)
- 17
- 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
- 40
- Möbius Function
- 1
- Radical
- 55
- 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
- yes
- 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
- no
- Narcissistic Number
- no
- Collatz Steps
- 112
- Smith Number
- no
Classification
- Natural
- yes
- Even
- no
- Odd
- yes
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
Names
- German
- fünfundfünfzig· ordinal: fünfundfünfzigste
- English
- fifty-five· ordinal: fifty-fifth
- Spanish
- cincuenta y cinco· ordinal: 55º
- French
- cinquante-cinq· ordinal: cinquante-cinqième
- Italian
- cinquantacinque· ordinal: 55º
- Latin
- quinquaginta quinque· ordinal: 55.
- Portuguese
- cinquenta e cinco· ordinal: 55º
Appears in sequences
- Mosaic numbers or multiplicative projection of n: if n = Product (p_j^k_j) then a(n) = Product (p_j * k_j).at n=54A000026
- The positive integers. Also called the natural numbers, the whole numbers or the counting numbers, but these terms are ambiguous.at n=54A000027
- Numbers that are not squares (or, the nonsquares).at n=47A000037
- Dying rabbits: a(0) = 1; for 1 <= n <= 12, a(n) = Fibonacci(n); for n >= 13, a(n) = a(n-1) + a(n-2) - a(n-13).at n=10A000044
- 1-digit numbers arranged in alphabetical order, then the 2-digit numbers arranged in alphabetical order, then the 3-digit numbers, etc.at n=25A000052
- A Beatty sequence: a(n) = floor(n/(e-2)).at n=39A000062
- -1 + number of partitions of n.at n=11A000065
- Odious numbers: numbers with an odd number of 1's in their binary expansion.at n=27A000069
- Lower Wythoff sequence (a Beatty sequence): a(n) = floor(n*phi), where phi = (1+sqrt(5))/2 = A001622.at n=33A000201
- a(8i+j) = 13i + a(j), where 1<=j<=8.at n=33A000202
- Nearest integer to e^n.at n=4A000227
- Remove all factors of 2 from n; or largest odd divisor of n; or odd part of n.at n=54A000265
- Square pyramidal numbers: a(n) = 0^2 + 1^2 + 2^2 + ... + n^2 = n*(n+1)*(2*n+1)/6.at n=5A000330
- Numbers where total number of 1-bits in the exponents of their prime factorization is even; a 2-way classification of integers: complement of A000028.at n=28A000379
- Numbers of form x^2 + 2y^2 + 2yz + 4z^2.at n=50A000398
- Numbers of form x^2 + y^2 + 2*z^2.at n=52A000401
- Numbers that are the sum of 4 nonzero squares.at n=40A000414
- The greedy sequence of integers which avoids 3-term geometric progressions.at n=40A000452
- 1 together with products of 2 or more distinct primes.at n=17A000469
- Heptagonal numbers (or 7-gonal numbers): n*(5*n-3)/2.at n=5A000566