The cubic root of 8 is 2.
It is the 5-th Fibonacci number F5.
It is a Jordan-Polya number, since it can be written as (2!)3.
It is a double factorial (8 = 4 !! = 2 ⋅ 4 ).
8 is nontrivially palindromic in base 3 and base 7.
8 is an esthetic number in base 6 and base 8, because in such bases it adjacent digits differ by 1.
It is a tau number, because it is divible by the number of its divisors (4).
It is an ABA number since it can be written as A⋅BA, here for A=2, B=2.
It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.
It is a Leyland number of the form 22 + 22.
It is an iccanobiF number.
8 is an idoneal number.
It is a tetranacci number.
It is an Ulam number.
8 is a strobogrammatic number because it is the same when read upside-down.
It is a O'Halloran number.
It is a Duffinian number.
8 is a nontrivial repdigit in base 3 and base 7.
It is a plaindrome in base 3, base 5, base 6 and base 7.
It is a nialpdrome in base 2, base 3, base 4, base 7 and base 8.
It is a zygodrome in base 3 and base 7.
It is a panconsummate number.
A polygon with 8 sides can be constructed with ruler and compass.
It is an impolite number, since it cannot be written as a nontrivial sum of consecutive naturals.
It is a (trivial) narcissistic number.
8 is the 2-nd octagonal number.
8 is the 2-nd centered heptagonal number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 8
8 is a wasteful number, since it uses less digits than its factorization.
8 is an odious number, because the sum of its binary digits is odd.
The square root of 8 is about 2.8284271247.