21305320265 has 16 divisors (see below), whose sum is σ = 25845144336. Its totient is φ = 16858752000.

The previous prime is 21305320249. The next prime is 21305320313. The reversal of 21305320265 is 56202350312.

It can be written as a sum of positive squares in 8 ways, for example, as 10324795321 + 10980524944 = 101611^2 + 104788^2 .

It is not a de Polignac number, because 21305320265 - 2⁴ = 21305320249 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 501245 + ... + 542085.

It is an arithmetic number, because the mean of its divisors is an integer number (1615321521).

Almost surely, 2^21305320265 is an apocalyptic number.

It is an amenable number.

21305320265 is a deficient number, since it is larger than the sum of its proper divisors (4539824071).

21305320265 is a wasteful number, since it uses less digits than its factorization.

21305320265 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41980.

The product of its (nonzero) digits is 10800, while the sum is 29.

Adding to 21305320265 its reverse (56202350312), we get a palindrome (77507670577).

The spelling of 21305320265 in words is "twenty-one billion, three hundred five million, three hundred twenty thousand, two hundred sixty-five".