7951
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 22
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 7952
- 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
- 7950
- Möbius Function
- -1
- Radical
- 7951
- 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
- 52
- 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
- 1005
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Number of monosubstituted alkanes C(n)H(2n+1)-X of the form shown in the Comments lines that are not stereoisomers.at n=20A000624
- Fibonacci numbers written backwards.at n=17A004091
- Reversals of Fibonacci numbers (sorted).at n=20A004170
- Numerator of [x^(2n+1)] of the Taylor expansion tanh(cosec(x) - cot(x)).at n=6A013524
- a(n) = Sum_{k=0..n} ceiling(k^3/n).at n=30A014813
- Fibonacci sequence beginning 5, 18.at n=14A022142
- Primes that remain prime through 3 iterations of function f(x) = 9x + 10.at n=30A023299
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 89.at n=3A031587
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 58 ones.at n=8A031826
- a(n) is the smallest prime such that a(1), ..., a(n-1) are squares mod a(n).at n=9A034698
- a(n) is square mod a(i), i < n.at n=16A034791
- Iccanobif (or iccanobiF) primes: primes which are Fibonacci numbers when reversed.at n=6A036797
- Primes p such that both p-2 and 2p-1 are prime.at n=43A038869
- Numbers whose base-4 representation contains exactly two 0's and four 3's.at n=19A045075
- Euclid-Mullin sequence (A000945) with initial value a(1)=19 instead of a(1)=2.at n=15A051312
- Prime lucky numbers k (from A031157) such that nextprime(k)=nextlucky(k).at n=12A057698
- Primes p such that x^53 = 2 has no solution mod p.at n=17A059258
- Minimum positive numerator of s_1/1 + ... + s_n/n in lowest terms, where each s_i equals 1 or -1.at n=24A061195
- Primes p such that (3*p)^2 + p^2 + 3^2 and (3*p)^2 - p^2 - 3^2 are both prime.at n=22A079796
- a(n)=A085956(3n).at n=24A086361