28506521 has 4 divisors (see below), whose sum is σ = 29201844. Its totient is φ = 27811200.

The previous prime is 28506503. The next prime is 28506523. The reversal of 28506521 is 12560582.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12560582 = 2 ⋅6280291.

It can be written as a sum of positive squares in 2 ways, for example, as 1466521 + 27040000 = 1211^2 + 5200^2 .

It is a cyclic number.

It is not a de Polignac number, because 28506521 - 2²² = 24312217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28506523) 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, 347600 + ... + 347681.

It is an arithmetic number, because the mean of its divisors is an integer number (7300461).

Almost surely, 2^28506521 is an apocalyptic number.

It is an amenable number.

28506521 is a deficient number, since it is larger than the sum of its proper divisors (695323).

28506521 is an equidigital number, since it uses as much as digits as its factorization.

28506521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 695322.

The product of its (nonzero) digits is 4800, while the sum is 29.

The square root of 28506521 is about 5339.1498386915. The cubic root of 28506521 is about 305.4790322433.

The spelling of 28506521 in words is "twenty-eight million, five hundred six thousand, five hundred twenty-one".