728406121 has 9 divisors (see below), whose sum is σ = 737505349. Its totient is φ = 719418784.

The previous prime is 728406061. The next prime is 728406127. The reversal of 728406121 is 121604827.

The square root of 728406121 is 26989.

It is a perfect power (a square), and thus also a powerful number.

728406121 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 324396121 + 404010000 = 18011^2 + 20100^2 .

It is not a de Polignac number, because 728406121 - 2¹⁵ = 728373353 is a prime.

It is a super-2 number, since 2×728406121² = 1061150954220533282, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (728406127) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3697395 + ... + 3697591.

Almost surely, 2^728406121 is an apocalyptic number.

728406121 is the 26989-th square number.

728406121 is the 13495-th centered octagonal number.

It is an amenable number.

728406121 is a deficient number, since it is larger than the sum of its proper divisors (9099228).

728406121 is an frugal number, since it uses more digits than its factorization.

728406121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668 (or 334 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 31.

The cubic root of 728406121 is about 899.7555389545.

It can be divided in two parts, 72840 and 6121, that added together give a square (78961 = 281²).

The spelling of 728406121 in words is "seven hundred twenty-eight million, four hundred six thousand, one hundred twenty-one".