28820521 has 4 divisors (see below), whose sum is σ = 29599492. Its totient is φ = 28041552.

The previous prime is 28820513. The next prime is 28820527. The reversal of 28820521 is 12502882.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19456921 + 9363600 = 4411^2 + 3060^2 .

It is a cyclic number.

It is not a de Polignac number, because 28820521 - 2³ = 28820513 is a prime.

It is a super-2 number, since 2×28820521² = 1661244861422882, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28820521.

It is not an unprimeable number, because it can be changed into a prime (28820527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 389430 + ... + 389503.

It is an arithmetic number, because the mean of its divisors is an integer number (7399873).

Almost surely, 2^28820521 is an apocalyptic number.

It is an amenable number.

28820521 is a deficient number, since it is larger than the sum of its proper divisors (778971).

28820521 is an equidigital number, since it uses as much as digits as its factorization.

28820521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 778970.

The product of its (nonzero) digits is 2560, while the sum is 28.

The square root of 28820521 is about 5368.4747368317. The cubic root of 28820521 is about 306.5965586165.

The spelling of 28820521 in words is "twenty-eight million, eight hundred twenty thousand, five hundred twenty-one".