28321728 has 56 divisors (see below), whose sum is σ = 79351632. Its totient is φ = 8884224.

The previous prime is 28321721. The next prime is 28321729. The reversal of 28321728 is 82712382.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28321721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1075 + ... + 7602.

Almost surely, 2^28321728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 28321728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39675816).

28321728 is an abundant number, since it is smaller than the sum of its proper divisors (51029904).

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

28321728 is a wasteful number, since it uses less digits than its factorization.

28321728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8709 (or 8699 counting only the distinct ones).

The product of its digits is 10752, while the sum is 33.

The square root of 28321728 is about 5321.8162313255. The cubic root of 28321728 is about 304.8175133398.

It can be divided in two parts, 2832 and 1728, that added together give a triangular number (4560 = T₉₅).

The spelling of 28321728 in words is "twenty-eight million, three hundred twenty-one thousand, seven hundred twenty-eight".