28289521 has 4 divisors (see below), whose sum is σ = 30465652. Its totient is φ = 26113392.

The previous prime is 28289519. The next prime is 28289531. The reversal of 28289521 is 12598282.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12598282 = 2 ⋅6299141.

It can be written as a sum of positive squares in 2 ways, for example, as 14930496 + 13359025 = 3864^2 + 3655^2 .

It is a cyclic number.

It is not a de Polignac number, because 28289521 - 2¹ = 28289519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28289501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1088046 + ... + 1088071.

It is an arithmetic number, because the mean of its divisors is an integer number (7616413).

Almost surely, 2^28289521 is an apocalyptic number.

It is an amenable number.

28289521 is a deficient number, since it is larger than the sum of its proper divisors (2176131).

28289521 is a wasteful number, since it uses less digits than its factorization.

28289521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2176130.

The product of its digits is 23040, while the sum is 37.

The square root of 28289521 is about 5318.7894299361. The cubic root of 28289521 is about 304.7019250379.

The spelling of 28289521 in words is "twenty-eight million, two hundred eighty-nine thousand, five hundred twenty-one".