2221
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 7
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 2222
- 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
- 2220
- Möbius Function
- -1
- Radical
- 2221
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 32
- 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
- 331
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes in ternary.at n=21A001363
- Artiads: the primes p == 1 (mod 5) for which Fibonacci((p-1)/5) is divisible by p.at n=14A001583
- Squares written in base 4.at n=13A001739
- Sextan primes: p = (x^6 + y^6)/(x^2 + y^2).at n=11A002647
- Largest label f(T) given to a rooted tree T with n nodes in Matula-Goebel labeling.at n=7A005518
- Number of paraffins.at n=20A005998
- From trees with valency <= 3.at n=7A006570
- Numbers that contain only 1's and 2's. Nonempty binary strings of length n in lexicographic order.at n=28A007931
- Coordination sequence T1 for Zeolite Code AFO.at n=31A008015
- Coordination sequence T3 for Zeolite Code AFO.at n=31A008017
- Coordination sequence T1 for Zeolite Code DAC.at n=30A008067
- Coordination sequence T1 for Zeolite Code HEU.at n=31A008116
- Coordination sequence T3 for Zeolite Code HEU.at n=31A008118
- Coordination sequence T3 for Zeolite Code DFO.at n=36A009877
- Coordination sequence T2 for Zeolite Code ZON.at n=33A009920
- a(n) = floor(n*(n - 1)*(n - 2)/31).at n=42A011913
- exp(cosh(x)*arcsin(x))=1+x+1/2!*x^2+5/3!*x^3+17/4!*x^4+65/5!*x^5...at n=7A012765
- Numbers k such that the continued fraction for sqrt(k) has period 27.at n=9A020366
- Primes that contain digits 1 and 2 only.at n=4A020450
- n-th prime p(k) such that p(k) + p(k+6) = p(k+2) + p(k+4).at n=35A022891