2157
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2880
- Proper Divisor Sum (Aliquot Sum)
- 723
- 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
- 1436
- Möbius Function
- 1
- Radical
- 2157
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 50
- Smith Number
- no
- Vampire 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
Appears in sequences
- Expansion of 1 / ((1-x)^2*(1-x^2)*(1-x^3)*(1-x^4)).at n=28A002621
- Crystal ball sequence for hexagonal close-packing.at n=8A007202
- Number of strict 7th-order maximal independent sets in path graph.at n=50A007386
- Coordination sequence T2 for Zeolite Code MTN.at n=28A008187
- Number of n-dimensional partitions of 5.at n=11A008779
- Coordination sequence for sigma-CrFe, Position Xb.at n=12A009960
- a(n) = n*(n-1) + (n-2)*(n-3) + ... + 1*0 + 1 for n odd; otherwise, a(n) = n*(n-1) + (n-2)*(n-3) + ... + 2*1.at n=22A014112
- a(n) = floor((Pi/2)^n).at n=17A014214
- Poincaré series [or Poincare series] for depths of roots in a certain root system.at n=11A019526
- Numbers k such that Fibonacci(k) == 2 (mod k).at n=35A023174
- s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (Lucas numbers), t = A014306.at n=26A024477
- a(n) = p(1)p(n) + p(2)p(n-1) + ... + p(k)p(n+1-k), where k = [ (n+1)/2 ], p = A000040 = the primes.at n=14A024697
- Golc sequence in base 2. Left to right concatenation of n,int(log_2(n)),int(log_2(int(log_2(n)))),... in base 2.at n=32A028432
- Size of lexicographic code of length n, Hamming distance 8 and weight 8.at n=30A030069
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 30.at n=19A031528
- Numbers k such that 75*2^k+1 is prime.at n=29A032387
- Number of ways of numbering the vertices of a cube so sum of the 8 numbers is n.at n=12A039959
- Numbers k such that string 5,5 occurs in the base 8 representation of k but not of k-1.at n=33A044232
- Numbers k such that the string 5,6 occurs in the base 9 representation of k but not of k-1.at n=29A044302
- Numbers n such that string 5,7 occurs in the base 10 representation of n but not of n-1.at n=23A044389