• 11 can be written using four 4's:
• 112 = 121 is the smallest square that contains exactly two digits '1'.
• When placing 8 queens on a 8×8 board, there can be at most 11 unattacked vacant squares. Two of the seven essentially distinct configurations:
11 is nontrivially palindromic in base 10.
11 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.
11 is an esthetic number in base 4, base 5, base 9 and base 11, because in such bases its adjacent digits differ by 1.
It is a strong prime.
It is a palprime.
It is a cyclic number.
It is a Sophie Germain prime.
It is a Chen prime.
It is a Lucas number.
It is the 5-th Jacobsthal number.
It is a magnanimous number.
It is an Ulam number.
11 is a strobogrammatic number because it is the same when read upside-down.
11 is strictly pandigital in base 3.
11 is a nontrivial repdigit in base 10.
It is a plaindrome in base 4, base 6, base 7, base 8, base 9 and base 10.
It is a nialpdrome in base 5, base 10 and base 11.
It is a zygodrome in base 10.
It is a panconsummate number.
It is a good prime.
It is equal to the Eulerian number A(4, 1).
11 is the 2-nd centered decagonal number.
11 is an equidigital number, since it uses as much as digits as its factorization.
11 is an odious number, because the sum of its binary digits is odd.
The square root of 11 is about 3.3166247904. The cubic root of 11 is about 2.2239800906.