1987
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 1988
- Proper Divisor Sum (Aliquot Sum)
- 1
- 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
- 1986
- Möbius Function
- -1
- Radical
- 1987
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- 94
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 300
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p of the form 3k+1 such that -sqrt(p) < sum_{x=1..p} cos(2*Pi*x^3/p) < sqrt(p).at n=45A000922
- Primes of the form m^2 + 3m + 9, where m can be positive or negative.at n=18A005471
- Coefficients of the '2nd-order' mock theta function A(q).at n=26A006304
- Number of n X 3 binary matrices under row and column permutations and column complementations.at n=13A006381
- Primes that divide at least one term of Sylvester's sequence s = A000058: s(n+1) = s(n)^2 - s(n) + 1, s(0) = 2.at n=14A007996
- Coordination sequence T1 for Zeolite Code AST.at n=32A008036
- Coordination sequence T3 for Zeolite Code MTW.at n=29A008198
- Least m such that if a/b < c/d are Farey fractions of order n then there exists k such that a/b < k/m < c/d, k/m reduced.at n=50A009571
- a(n) = prime(n*(n+1)/2).at n=23A011756
- Smallest nonempty set S containing prime divisors of 5k+2 for each k in S.at n=29A020596
- Smallest nonempty set S containing prime divisors of 7k+6 for each k in S.at n=44A020611
- Smallest nonempty set S containing prime divisors of 10k+4 for each k in S.at n=30A020634
- Primes that remain prime through 2 iterations of function f(x) = x + 6.at n=49A023241
- a(n) = Sum_{k=1..n} k*floor(n/k); also Sum_{k=1..n} sigma(k) where sigma(n) = sum of divisors of n (A000203).at n=48A024916
- a(n) = (d(n)-r(n))/2, where d = A026060 and r is the periodic sequence with fundamental period (1,0,0,0).at n=20A026061
- a(n) = n^2 + n + 7.at n=44A027692
- Q(sqrt(n)) has class number 3.at n=40A029703
- Primes that are palindromic in base 13.at n=28A029980
- Numbers having period-2 7-digitized sequences.at n=41A031202
- a(n) = prime(10*n).at n=29A031343