728223921 has 6 divisors (see below), whose sum is σ = 1051879010. Its totient is φ = 485482608.

The previous prime is 728223913. The next prime is 728223931. The reversal of 728223921 is 129322827.

It can be written as a sum of positive squares in only one way, i.e., 665640000 + 62583921 = 25800^2 + 7911^2 .

It is not a de Polignac number, because 728223921 - 2³ = 728223913 is a prime.

It is a super-2 number, since 2×728223921² = 1060620158233228482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (728223931) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 40456876 + ... + 40456893.

Almost surely, 2^728223921 is an apocalyptic number.

It is an amenable number.

728223921 is a deficient number, since it is larger than the sum of its proper divisors (323655089).

728223921 is a wasteful number, since it uses less digits than its factorization.

728223921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80913775 (or 80913772 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 728223921 is about 26985.6243396368. The cubic root of 728223921 is about 899.6805125257.

The spelling of 728223921 in words is "seven hundred twenty-eight million, two hundred twenty-three thousand, nine hundred twenty-one".