28331721 has 16 divisors (see below), whose sum is σ = 45789120. Its totient is φ = 17170560.

The previous prime is 28331701. The next prime is 28331747. The reversal of 28331721 is 12713382.

It is not a de Polignac number, because 28331721 - 2⁵ = 28331689 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (28331701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47400 + ... + 47993.

It is an arithmetic number, because the mean of its divisors is an integer number (2861820).

Almost surely, 2^28331721 is an apocalyptic number.

It is an amenable number.

28331721 is a deficient number, since it is larger than the sum of its proper divisors (17457399).

28331721 is a wasteful number, since it uses less digits than its factorization.

28331721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95413 (or 95407 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 28331721 is about 5322.7550197243. The cubic root of 28331721 is about 304.8533595898.

It can be divided in two parts, 2833 and 1721, that added together give a palindrome (4554).

The spelling of 28331721 in words is "twenty-eight million, three hundred thirty-one thousand, seven hundred twenty-one".