45
domain: N
Properties
Digital Properties
- Digit Count
- 2
- Digit Sum
- 9
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- yes
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 78
- Proper Divisor Sum (Aliquot Sum)
- 33
- 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
- 24
- Möbius Function
- 0
- Radical
- 15
- Omega Function (Ω)
- 3
- 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
- yes
- Perfect Square
- no
- Perfect Cube
- no
- Pentagonal Number
- no
- Hexagonal Number
- yes
- 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
- 16
- Smith Number
- no
Classification
- Natural
- yes
- Even
- no
- Odd
- 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
- yes
- Carmichael Number
- no
Names
- German
- fünfundvierzig· ordinal: fünfundvierzigste
- English
- forty-five· ordinal: forty-fifth
- Spanish
- cuarenta y cinco· ordinal: 45º
- French
- quarante-cinq· ordinal: quarante-cinqième
- Italian
- quarantacinque· ordinal: 45º
- Latin
- quadraginta quinque· ordinal: 45.
- Portuguese
- quarenta e cinco· ordinal: 45º
Appears in sequences
- The positive integers. Also called the natural numbers, the whole numbers or the counting numbers, but these terms are ambiguous.at n=44A000027
- Numbers that are not squares (or, the nonsquares).at n=38A000037
- 1-digit numbers arranged in alphabetical order, then the 2-digit numbers arranged in alphabetical order, then the 3-digit numbers, etc.at n=35A000052
- Numbers k such that (2k)^4 + 1 is prime.at n=16A000059
- A Beatty sequence: a(n) = floor(n/(e-2)).at n=32A000062
- a(n) = Sum_{k=0..n} p(k) where p(k) = number of partitions of k (A000041).at n=7A000070
- Number of trees of diameter 4.at n=11A000094
- Denumerants: Expansion of 1/((1-x)*(1-x^2)*(1-x^5)).at n=26A000115
- Number of partitions into non-integral powers.at n=5A000148
- Lower Wythoff sequence (a Beatty sequence): a(n) = floor(n*phi), where phi = (1+sqrt(5))/2 = A001622.at n=27A000201
- a(8i+j) = 13i + a(j), where 1<=j<=8.at n=27A000202
- Number of positive integers <= 2^n of form x^2 + 3 y^2.at n=7A000205
- Rencontres numbers: number of permutations of [n] with exactly one fixed point.at n=4A000240
- Number of permutations in the symmetric group S_n that have odd order.at n=5A000246
- Number of symmetric reflexive relations on n nodes: (1/2)*A000666.at n=3A000250
- Remove all factors of 2 from n; or largest odd divisor of n; or odd part of n.at n=44A000265
- Number of 4-dimensional partitions of n.at n=3A000334
- Euler transform of A000292.at n=3A000335
- Number of partitions into non-integral powers.at n=3A000339
- Triangle of numbers related to triangle A049213; generalization of Stirling numbers of second kind A008277, Bessel triangle A001497.at n=19A000369