87
domain: N
Properties
Digital Properties
- Digit Count
- 2
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 120
- 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
- 56
- Möbius Function
- 1
- Radical
- 87
- 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
- 30
- 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
- siebenundachtzig· ordinal: siebenundachtzigste
- English
- eighty-seven· ordinal: eighty-seventh
- Spanish
- ochenta y siete· ordinal: 87º
- French
- quatre-vingt-sept· ordinal: quatre-vingt-septième
- Italian
- ottantasette· ordinal: 87º
- Latin
- octoginta septem· ordinal: 87.
- Portuguese
- oitenta e sete· ordinal: 87º
Appears in sequences
- Numbers that are not squares (or, the nonsquares).at n=77A000037
- Number of integers <= 2^n of form x^2 - 2y^2.at n=8A000047
- 1-digit numbers arranged in alphabetical order, then the 2-digit numbers arranged in alphabetical order, then the 3-digit numbers, etc.at n=17A000052
- Numbers k such that (2k)^4 + 1 is prime.at n=25A000059
- A Beatty sequence: a(n) = floor(n/(e-2)).at n=62A000062
- Odious numbers: numbers with an odd number of 1's in their binary expansion.at n=43A000069
- Positive zeros of Bessel function of order 0 rounded to nearest integer.at n=27A000134
- Lower Wythoff sequence (a Beatty sequence): a(n) = floor(n*phi), where phi = (1+sqrt(5))/2 = A001622.at n=53A000201
- a(8i+j) = 13i + a(j), where 1<=j<=8.at n=53A000202
- A Beatty sequence: floor(n*(e-1)).at n=50A000210
- 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=45A000379
- The greedy sequence of integers which avoids 3-term geometric progressions.at n=64A000452
- 1 together with products of 2 or more distinct primes.at n=31A000469
- Number of n-step spiral self-avoiding walks on hexagonal lattice, where at each step one may continue in same direction or make turn of 2*Pi/3 counterclockwise.at n=12A000511
- Number of symmetric ways of folding a strip of n labeled stamps.at n=5A000560
- Number of partitions of n into distinct primes.at n=79A000586
- Number of nonnegative solutions to x^2 + y^2 + z^2 <= n.at n=22A000606
- Number of nonnegative solutions to x^2 + y^2 + z^2 <= n.at n=23A000606
- Number of partitions of n into prime parts.at n=29A000607
- Expansion of Product_{k>=0} (1 + x^(2k+1)); number of partitions of n into distinct odd parts; number of self-conjugate partitions; number of symmetric Ferrers graphs with n nodes.at n=48A000700