• 728 can be written using four 4's:

See also 113.

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728 has 16 divisors (see below), whose sum is σ = 1680. Its totient is φ = 288.

The previous prime is 727. The next prime is 733. The reversal of 728 is 827.

728 = 7² + 8² + ... + 13².

728 is nontrivially palindromic in base 3 and base 9.

728 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Cunningham number, because it is equal to 3⁶-1.

728 is an esthetic number in base 6, because in such base its adjacent digits differ by 1.

It is a Smith number, since the sum of its digits (17) coincides with the sum of the digits of its prime factors.

It is a nude number because it is divisible by every one of its digits.

It is one of the 548 Lynch-Bell numbers.

728 is a nontrivial repdigit in base 3 and base 9.

It is a plaindrome in base 3, base 9 and base 15.

It is a nialpdrome in base 3, base 9 and base 13.

It is a zygodrome in base 3 and base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50 + ... + 62.

It is an arithmetic number, because the mean of its divisors is an integer number (105).

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (840).

728 is an abundant number, since it is smaller than the sum of its proper divisors (952).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

728 is a wasteful number, since it uses less digits than its factorization.

728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26 (or 22 counting only the distinct ones).

The product of its digits is 112, while the sum is 17.

The square root of 728 is about 26.9814751265. The cubic root of 728 is about 8.9958828906.

Subtracting from 728 its product of digits (112), we obtain a palindrome (616).

Subtracting 728 from its reverse (827), we obtain a palindrome (99).

It can be divided in two parts, 72 and 8, that multiplied together give a square (576 = 24²).

The spelling of 728 in words is "seven hundred twenty-eight", and thus it is an aban number and an oban number.