28721221524 has 72 divisors (see below), whose sum is σ = 73226953800. Its totient is φ = 9491427072.

The previous prime is 28721221471. The next prime is 28721221531. The reversal of 28721221524 is 42512212782.

It is a happy number.

28721221524 is a `hidden beast` number, since 2 + 8 + 7 + 2 + 122 + 1 + 524 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 2418869124 + 26302352400 = 49182^2 + 162180^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2982942 + ... + 2992554.

It is an arithmetic number, because the mean of its divisors is an integer number (1017041025).

Almost surely, 2^28721221524 is an apocalyptic number.

It is an amenable number.

28721221524 is an abundant number, since it is smaller than the sum of its proper divisors (44505732276).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28721221524 is a wasteful number, since it uses less digits than its factorization.

28721221524 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10329 (or 10324 counting only the distinct ones).

The product of its digits is 35840, while the sum is 36.

The spelling of 28721221524 in words is "twenty-eight billion, seven hundred twenty-one million, two hundred twenty-one thousand, five hundred twenty-four".