28921728 has 128 divisors (see below), whose sum is σ = 86365440. Its totient is φ = 8499200.

The previous prime is 28921727. The next prime is 28921771. The reversal of 28921728 is 82712982.

It is a tau number, because it is divible by the number of its divisors (128).

Its product of digits (32256) is a multiple of the sum of its prime divisors (224).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28921723) 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, 173101 + ... + 173267.

It is an arithmetic number, because the mean of its divisors is an integer number (674730).

Almost surely, 2^28921728 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 28921728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43182720).

28921728 is an abundant number, since it is smaller than the sum of its proper divisors (57443712).

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

28921728 is a wasteful number, since it uses less digits than its factorization.

28921728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236 (or 224 counting only the distinct ones).

The product of its digits is 32256, while the sum is 39.

The square root of 28921728 is about 5377.8925240283. The cubic root of 28921728 is about 306.9550238802.

The spelling of 28921728 in words is "twenty-eight million, nine hundred twenty-one thousand, seven hundred twenty-eight".