21805043505 has 32 divisors (see below), whose sum is σ = 40799345664. Its totient is φ = 9736203456.

The previous prime is 21805043503. The next prime is 21805043551. The reversal of 21805043505 is 50534050812.

It is not a de Polignac number, because 21805043505 - 2¹ = 21805043503 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21805043501) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2410219 + ... + 2419248.

It is an arithmetic number, because the mean of its divisors is an integer number (1274979552).

Almost surely, 2^21805043505 is an apocalyptic number.

It is an amenable number.

21805043505 is a deficient number, since it is larger than the sum of its proper divisors (18994302159).

21805043505 is a wasteful number, since it uses less digits than its factorization.

21805043505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4829525.

The product of its (nonzero) digits is 24000, while the sum is 33.

The spelling of 21805043505 in words is "twenty-one billion, eight hundred five million, forty-three thousand, five hundred five".