2155
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2592
- Proper Divisor Sum (Aliquot Sum)
- 437
- 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
- 1720
- Möbius Function
- 1
- Radical
- 2155
- 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
- 169
- Smith Number
- yes
- 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
- Prime numbers of measurement.at n=43A002049
- From the graph reconstruction problem.at n=5A006655
- Coordination sequence T1 for Zeolite Code AET.at n=32A008007
- Coordination sequence T1 for Zeolite Code SGT.at n=29A008229
- Smallest number whose cube has n digits.at n=10A018005
- Number of balls in pyramid with base either a regular hexagon or a hexagon with alternate sides differing by 1 (balls in hexagonal pyramid of height n taken from hexagonal close-packing).at n=20A019298
- Numbers k such that the continued fraction for sqrt(k) has period 32.at n=31A020371
- Every prefix prime in base 6 (written in base 6).at n=16A024766
- Partial sums of the sequence of prime powers (A000961).at n=42A024918
- T(2n-1,n-1), T given by A026568.at n=6A026577
- T(n,[ n/2 ]), T given by A026568.at n=13A026579
- a(n) = T(2*n-1, n-1), where T is given by A026584.at n=6A026593
- a(n) = T(n, floor(n/2)), where T is given by A026584.at n=13A026595
- a(n) is the square root of A030676(n).at n=54A030677
- Cube root of A030697.at n=9A030698
- 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 18.at n=43A031516
- Number of partitions of n with equal nonzero number of parts congruent to each of 0, 3 and 4 (mod 5).at n=43A035587
- Numbers n such that digit sum of n equals digit sum of 'juxtaposition' and 'sum' of its prime factors (counted with multiplicity).at n=38A036921
- Odd composite numbers n such that the digit sum of n equals digit sum of sum of its prime factors (counted with multiplicity).at n=25A036923
- Digit sum of composite odd number equals digit sum of juxtaposition of its prime factors (counted with multiplicity).at n=36A036925