2102
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 5
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 3156
- Proper Divisor Sum (Aliquot Sum)
- 1054
- 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
- 1050
- Möbius Function
- 1
- Radical
- 2102
- 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
- 94
- 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
- yes
- Odd
- no
Appears in sequences
- Numbers k such that 2*25^k - 1 is prime.at n=12A002958
- Greatest k such that binomial(k,n) has fewer than n distinct prime factors.at n=21A005735
- Number of partitions of n into partition numbers.at n=40A007279
- Coordination sequence T1 for Zeolite Code KFI.at n=35A008123
- Coordination sequence T2 for Zeolite Code -CLO.at n=40A009851
- a(0) = 1, a(n) = 21*n^2 + 2 for n>0.at n=10A010011
- Numbers k such that the continued fraction for sqrt(k) has period 34.at n=17A020373
- Least k such that b(k) = n, where b( ) is sequence A020944.at n=47A020948
- Fibonacci sequence beginning 1, 23.at n=11A022393
- n written in fractional base 3/2.at n=11A024629
- Coordination sequence T1 for Zeolite Code CGS.at n=34A027365
- 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 44.at n=13A031542
- a(n) = floor(5*n^2/2).at n=29A032526
- Trajectory of 1 under map n->21n+1 if n odd, n->n/2 if n even.at n=16A033967
- Roots of 'non-palindromic squares remaining square when written backwards'.at n=42A035123
- Trajectory of 3 under map n->21*n+1 if n odd, n->n/2 if n even.at n=23A037108
- Numbers whose base-2 and base-10 expansions have the same digit sum.at n=40A037308
- Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,1,0.at n=3A037527
- Base 3 digits are, in order, the first n terms of the periodic sequence with initial period 2,2,1.at n=6A037560
- a(n)=(s(n)+8)/10, where s(n)=n-th base 10 palindrome that starts with 2.at n=32A043081