21305522665 has 36 divisors (see below), whose sum is σ = 29949356556. Its totient is φ = 14507746176.

The previous prime is 21305522657. The next prime is 21305522677. The reversal of 21305522665 is 56622550312.

It can be written as a sum of positive squares in 6 ways, for example, as 2368184896 + 18937337769 = 48664^2 + 137613^2 .

It is not a de Polignac number, because 21305522665 - 2³ = 21305522657 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 5437287 + ... + 5441203.

It is an arithmetic number, because the mean of its divisors is an integer number (831926571).

Almost surely, 2^21305522665 is an apocalyptic number.

It is an amenable number.

21305522665 is a deficient number, since it is larger than the sum of its proper divisors (8643833891).

21305522665 is an equidigital number, since it uses as much as digits as its factorization.

21305522665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4234 (or 4078 counting only the distinct ones).

The product of its (nonzero) digits is 108000, while the sum is 37.

The spelling of 21305522665 in words is "twenty-one billion, three hundred five million, five hundred twenty-two thousand, six hundred sixty-five".