21528131840 has 36 divisors (see below), whose sum is σ = 51566606364. Its totient is φ = 8611252224.

The previous prime is 21528131827. The next prime is 21528131881. The reversal of 21528131840 is 4813182512.

It can be written as a sum of positive squares in 2 ways, for example, as 9704614144 + 11823517696 = 98512^2 + 108736^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21528131840.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8408147 + ... + 8410706.

Almost surely, 2^21528131840 is an apocalyptic number.

21528131840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21528131840 is an abundant number, since it is smaller than the sum of its proper divisors (30038474524).

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

21528131840 is an equidigital number, since it uses as much as digits as its factorization.

21528131840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16818874 (or 16818860 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 35.

The spelling of 21528131840 in words is "twenty-one billion, five hundred twenty-eight million, one hundred thirty-one thousand, eight hundred forty".