28537821 has 24 divisors (see below), whose sum is σ = 44717400. Its totient is φ = 17433216.

The previous prime is 28537801. The next prime is 28537823. The reversal of 28537821 is 12873582.

28537821 is a `hidden beast` number, since 285 + 378 + 2 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 2924100 + 25613721 = 1710^2 + 5061^2 .

It is not a de Polignac number, because 28537821 - 2¹⁰ = 28536797 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28537823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 16615 + ... + 18251.

It is an arithmetic number, because the mean of its divisors is an integer number (1863225).

Almost surely, 2^28537821 is an apocalyptic number.

It is an amenable number.

28537821 is a deficient number, since it is larger than the sum of its proper divisors (16179579).

28537821 is a wasteful number, since it uses less digits than its factorization.

28537821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1805 (or 1802 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 28537821 is about 5342.0802128010. The cubic root of 28537821 is about 305.5907961020.

The spelling of 28537821 in words is "twenty-eight million, five hundred thirty-seven thousand, eight hundred twenty-one".