21521157728 has 48 divisors (see below), whose sum is σ = 50971173120. Its totient is φ = 8737911936.

The previous prime is 21521157727. The next prime is 21521157751. The reversal of 21521157728 is 82775112512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521157727) 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 7 ways as a sum of consecutive naturals, for example, 2524076 + ... + 2532587.

It is an arithmetic number, because the mean of its divisors is an integer number (1061899440).

Almost surely, 2^21521157728 is an apocalyptic number.

21521157728 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21521157728 is an abundant number, since it is smaller than the sum of its proper divisors (29450015392).

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

21521157728 is a wasteful number, since it uses less digits than its factorization.

21521157728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5056699 (or 5056691 counting only the distinct ones).

The product of its digits is 78400, while the sum is 41.

The spelling of 21521157728 in words is "twenty-one billion, five hundred twenty-one million, one hundred fifty-seven thousand, seven hundred twenty-eight".