2689
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 2690
- 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
- 2688
- Möbius Function
- -1
- Radical
- 2689
- 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
- 71
- 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
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 391
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Genus of modular group Gamma(n) = genus of modular curve Chi(n).at n=46A001767
- Smallest prime p of form p = 8k+1 such that first n primes (p_1=2, ..., p_n) are quadratic residues mod p.at n=4A002224
- Primes p == 1 (mod 8), p = a^2 + 64*b^2 such that y^2 = x^3 + p*x has rank 2.at n=35A007766
- Coordination sequence T10 for Zeolite Code MFI.at n=33A008162
- Coordination sequence T7 for Zeolite Code MFI.at n=33A008170
- Coordination sequence T2 for Zeolite Code TON.at n=32A008242
- Coordination sequence T6 for Zeolite Code VNI.at n=32A009912
- Primes p == 1 mod 8 such that 2 and -2 are both 4th powers (one implies other) mod p.at n=44A014754
- Quadruples of different integers from [ 1,n ] with no common factors between triples.at n=18A015625
- Numbers k such that the continued fraction for sqrt(k) has period 85.at n=0A020424
- Let q_k = p*(p+2) be product of k-th pair of twin primes; sequence gives values of p+2 such that (q_k)^2 > q_{k-i}*q_{k+i} for all 1 <= i <= k-1.at n=25A021007
- Primes that remain prime through 2 iterations of function f(x) = 9x + 2.at n=39A023265
- Numbers whose least quadratic nonresidue (A020649) is 13.at n=7A025025
- a(n) is the least odd prime p such that the maximum run length of consecutive quadratic residues modulo p is n.at n=23A025046
- Primes such that in p^2 the parity of digits alternates.at n=31A030145
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 40 ones.at n=5A031808
- Lucky numbers with size of gaps equal to 8 (lower terms).at n=29A031890
- Lucky numbers with size of gaps equal to 18 (upper terms).at n=18A031901
- a(n) = prime(10*n-9).at n=39A031920
- Primes of the form x^2+74*y^2.at n=15A033248