2521
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 2522
- 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
- 2520
- Möbius Function
- -1
- Radical
- 2521
- 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
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 40
- 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
- 369
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p of the form 3k+1 such that sum_{x=1..p} cos(2*Pi*x^3/p) < -sqrt(p).at n=34A000923
- Numbers k such that k^2 is centered hexagonal.at n=3A001570
- Squares written in base 6.at n=25A001741
- Centered square numbers: a(n) = 2*n*(n+1)+1. Sums of two consecutive squares. Also, consider all Pythagorean triples (X, Y, Z=Y+1) ordered by increasing Z; then sequence gives Z values.at n=35A001844
- Centered 12-gonal numbers, or centered dodecagonal numbers: numbers of the form 6*k*(k-1) + 1.at n=20A003154
- Coding Fibonacci numbers.at n=4A005205
- Primitive prime factors of the sequence k^2 + 1 (A002522) in the order that they are found.at n=50A005529
- Number of acyclic ethylene derivatives with n carbon atoms.at n=9A005959
- Related to self-avoiding walks on square lattice.at n=6A006814
- Coordination sequence T6 for Zeolite Code EUO.at n=31A008101
- Numbers k such that 3^k - 2 is prime.at n=21A014224
- 3 and -3 are both 4th powers (one implies other) mod these primes p=1 mod 8.at n=16A014755
- Coordination sequence T8 for Zeolite Code TER.at n=34A016440
- Numbers k such that the continued fraction for sqrt(k) has period 67.at n=2A020406
- Primes that remain prime through 2 iterations of the function f(x) = 2x + 9.at n=44A023245
- Primes that remain prime through 2 iterations of the function f(x) = 5x + 8.at n=28A023255
- Primes that remain prime through 2 iterations of function f(x) = 9x + 10.at n=43A023268
- Primes that remain prime through 3 iterations of function f(x) = 2x + 9.at n=9A023276
- Primes that remain prime through 3 iterations of function f(x) = 5x + 8.at n=8A023286
- Primes that remain prime through 3 iterations of function f(x) = 9x + 10.at n=14A023299