21805597853 has 4 divisors (see below), whose sum is σ = 23482951548. Its totient is φ = 20128244160.

The previous prime is 21805597841. The next prime is 21805597921. The reversal of 21805597853 is 35879550812.

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 2324975524 + 19480622329 = 48218^2 + 139573^2 .

It is a cyclic number.

It is not a de Polignac number, because 21805597853 - 2⁶ = 21805597789 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21805597795 and 21805597804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21805597823) 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, 838676828 + ... + 838676853.

It is an arithmetic number, because the mean of its divisors is an integer number (5870737887).

Almost surely, 2^21805597853 is an apocalyptic number.

It is an amenable number.

21805597853 is a deficient number, since it is larger than the sum of its proper divisors (1677353695).

21805597853 is a wasteful number, since it uses less digits than its factorization.

21805597853 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1677353694.

The product of its (nonzero) digits is 3024000, while the sum is 53.

The spelling of 21805597853 in words is "twenty-one billion, eight hundred five million, five hundred ninety-seven thousand, eight hundred fifty-three".