7561
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 7562
- 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
- 7560
- Möbius Function
- -1
- Radical
- 7561
- 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
- 83
- 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
- 960
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Markoff (or Markov) numbers: union of positive integers x, y, z satisfying x^2 + y^2 + z^2 = 3*x*y*z.at n=19A002559
- Centered 12-gonal numbers, or centered dodecagonal numbers: numbers of the form 6*k*(k-1) + 1.at n=35A003154
- a(n) = least m such that if r and s in {1/2, 1/4, 1/6, ..., 1/2n} satisfy r < s, then r < k/m < (k+2)/m < s for some integer k.at n=37A024842
- Numbers whose least quadratic nonresidue (A020649) is 13.at n=21A025025
- Smallest prime that is simultaneously of forms x^2 + m*y^2 for m = 1, ..., n.at n=10A028372
- Smallest prime that is simultaneously of forms x^2 + m*y^2 for m = 1, ..., n.at n=11A028372
- Primes of the form k^2 - 8.at n=19A028886
- Numbers k such that binomial(2k,k) is not divisible by 3, 5 or 7.at n=10A030979
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 70 ones.at n=5A031838
- Numbers k such that 251*2^k+1 is prime.at n=11A032502
- Numbers whose set of base-9 digits is {1,3}.at n=36A032916
- Primes p such that both p-2 and 2p-1 are prime.at n=42A038869
- Denominators of continued fraction convergents to sqrt(11).at n=6A041015
- Denominators of continued fraction convergents to sqrt(44).at n=14A041075
- Denominators of continued fraction convergents to sqrt(99).at n=6A041179
- Largest prime substring in 7^n (0 if none).at n=15A046273
- Primes p such that number of primes produced according to rules stipulated in Honaker's A048853 is 3.at n=12A050665
- First member of a prime triple in a 2p-1 progression.at n=36A057326
- Distinct (non-overlapping) twin Harshad numbers whose sum is prime.at n=32A060288
- Primes which are sums of twin Harshad numbers (includes overlaps).at n=37A060290