7221
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 12
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 10080
- Proper Divisor Sum (Aliquot Sum)
- 2859
- 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
- 4592
- Möbius Function
- -1
- Radical
- 7221
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- 57
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- a(n) = 1 + n/2 + 9*n^2/2.at n=40A006137
- a(n) = A024727(n+3)/4.at n=13A024728
- Number of powerful numbers between 2^(n-1)+1 and 2^n.at n=27A062761
- a(n) = (2*n+5)*(2*n+1).at n=41A078371
- a(n) = (4*n+3)*(4*n+7).at n=20A085027
- Number of partitions of n into nonsquares.at n=48A087153
- Numbers of the form 1+(1+p)*p^e, p prime and e>0.at n=45A087195
- a(n) = n^3 + n^2 + 1.at n=19A098547
- Numbers of the form a^5 + b^4 with a, b > 0.at n=42A100294
- Positions where A109890(n) = Sum_{i = 1..n-1} A109890(i).at n=23A111315
- a(n) = Sum_{k=1..n} floor(n^2/k).at n=41A118014
- Numbers k which divide the sum of the Fibonacci numbers F(1) through F(k) and such that k is not a multiple of 24.at n=9A124456
- Number of prime 5-tuples up to 10^n.at n=8A125517
- Digital sum of the 2^n-th partition number.at n=21A129491
- a(n) = a(n-1) + a(floor(n/2)) + a(ceiling(n/2)).at n=27A131205
- Third trisection of A061037.at n=27A142600
- a(n) = (8*n+3)*(8*n+7).at n=10A146301
- a(n) = 100*n^2 + 100*n + 21.at n=8A152161
- a(n) = 361*n + 1.at n=19A158310
- a(n) = 20*n^2 + 1.at n=19A158493