28128915 has 12 divisors (see below), whose sum is σ = 48756864. Its totient is φ = 15002064.

The previous prime is 28128913. The next prime is 28128929. The reversal of 28128915 is 51982182.

It is not a de Polignac number, because 28128915 - 2¹ = 28128913 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 28128915.

It is not an unprimeable number, because it can be changed into a prime (28128913) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 312499 + ... + 312588.

It is an arithmetic number, because the mean of its divisors is an integer number (4063072).

Almost surely, 2^28128915 is an apocalyptic number.

28128915 is a deficient number, since it is larger than the sum of its proper divisors (20627949).

28128915 is a wasteful number, since it uses less digits than its factorization.

28128915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 625098 (or 625095 counting only the distinct ones).

The product of its digits is 11520, while the sum is 36.

The square root of 28128915 is about 5303.6699557948. The cubic root of 28128915 is about 304.1242098326.

The spelling of 28128915 in words is "twenty-eight million, one hundred twenty-eight thousand, nine hundred fifteen".