21805885537 has 4 divisors (see below), whose sum is σ = 21807132676. Its totient is φ = 21804638400.

The previous prime is 21805885511. The next prime is 21805885589. The reversal of 21805885537 is 73558850812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18348327936 + 3457557601 = 135456^2 + 58801^2 .

It is a cyclic number.

It is not a de Polignac number, because 21805885537 - 2¹⁵ = 21805852769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21805885337) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 596964 + ... + 632437.

It is an arithmetic number, because the mean of its divisors is an integer number (5451783169).

Almost surely, 2^21805885537 is an apocalyptic number.

It is an amenable number.

21805885537 is a deficient number, since it is larger than the sum of its proper divisors (1247139).

21805885537 is a wasteful number, since it uses less digits than its factorization.

21805885537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1247138.

The product of its (nonzero) digits is 2688000, while the sum is 52.

The spelling of 21805885537 in words is "twenty-one billion, eight hundred five million, eight hundred eighty-five thousand, five hundred thirty-seven".