721128 has 16 divisors (see below), whose sum is σ = 1802880. Its totient is φ = 240368.

The previous prime is 721117. The next prime is 721129. The reversal of 721128 is 821127.

It is not an unprimeable number, because it can be changed into a prime (721129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15000 + ... + 15047.

It is an arithmetic number, because the mean of its divisors is an integer number (112680).

2⁷²¹¹²⁸ is an apocalyptic number.

It is an amenable number.

721128 is an abundant number, since it is smaller than the sum of its proper divisors (1081752).

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

721128 is a wasteful number, since it uses less digits than its factorization.

721128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30056 (or 30052 counting only the distinct ones).

The product of its digits is 224, while the sum is 21.

The square root of 721128 is about 849.1925576688. The cubic root of 721128 is about 89.6748762923.

Subtracting 721128 from its reverse (821127), we obtain a palindrome (99999).

The spelling of 721128 in words is "seven hundred twenty-one thousand, one hundred twenty-eight".