1001
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 2
- Digital Root
- 2
- Palindromic Number
- yes
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 1344
- Proper Divisor Sum (Aliquot Sum)
- 343
- 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
- 720
- Möbius Function
- -1
- Radical
- 1001
- 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
- yes
- 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
- 142
- 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
- -1 + number of partitions of n.at n=22A000065
- a(n) = 3*(2*n)!/((n+2)!*(n-1)!).at n=7A000245
- Pentagonal numbers: a(n) = n*(3*n-1)/2.at n=26A000326
- Binomial coefficient binomial(n,4) = n*(n-1)*(n-2)*(n-3)/24.at n=14A000332
- a(n) = 5*binomial(2n, n-2)/(n+3).at n=5A000344
- Numbers written in base of triangular numbers.at n=10A000462
- a(0)=1; a(n) = 10^n + 1, n >= 1.at n=3A000533
- Number of numbers == 0 (mod 3) in range 2^n to 2^(n+1) with odd number of 1's in binary expansion.at n=12A000773
- Strobogrammatic numbers: the same upside down.at n=19A000787
- a(n) = n^3 + 1.at n=11A001093
- a(1)=0, a(2n) = a(n)+1, a(2n+1) = 10*a(n+1).at n=17A001202
- a(n) = binomial coefficient C(n,10).at n=4A001287
- Generalized pentagonal numbers: m*(3*m - 1)/2, m = 0, +-1, +-2, +-3, ....at n=51A001318
- Number of n-node rooted trees of height at most 3.at n=13A001383
- Numbers with an even number of digits.at n=91A001637
- a(n) is 9 written in base 10-n.at n=8A001731
- Squares written in base 2.at n=3A001737
- Genus of modular group Gamma(n) = genus of modular curve Chi(n).at n=29A001767
- a(n) = n*a(n-1) + (n-4)*a(n-2), a(2) = 0, a(3) = 1.at n=5A001909
- Palindromic pentagonal numbers.at n=4A002069