• 57 can be written using four 4's:
57 is nontrivially palindromic in base 5 and base 7.
57 is an esthetic number in base 4, base 5 and base 13, because in such bases its adjacent digits differ by 1.
It is a Leyland number of the form 52 + 25.
57 is an idoneal number.
It is an Ulam number.
It is a D-number.
It is the 8-th Hogben number.
It is a Duffinian number.
57 is an undulating number in base 5.
57 is a nontrivial repdigit in base 7.
It is a plaindrome in base 6, base 7, base 10, base 12, base 13, base 15 and base 16.
It is a nialpdrome in base 4, base 7, base 8, base 9, base 11 and base 14.
It is a zygodrome in base 7.
It is a panconsummate number.
It is equal to the Eulerian number A(6, 1).
It is an amenable number.
57 is a wasteful number, since it uses less digits than its factorization.
57 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 22.
The square root of 57 is about 7.5498344353. The cubic root of 57 is about 3.8485011313.
Subtracting from 57 its sum of digits (12), we obtain a triangular number (45 = T9).
Subtracting from 57 its product of digits (35), we obtain a palindrome (22).