21665593853 has 4 divisors (see below), whose sum is σ = 21667582140. Its totient is φ = 21663605568.

The previous prime is 21665593819. The next prime is 21665593897. The reversal of 21665593853 is 35839556612.

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 12006242329 + 9659351524 = 109573^2 + 98282^2 .

It is a cyclic number.

It is not a de Polignac number, because 21665593853 - 2¹⁶ = 21665528317 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21665593795 and 21665593804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665599853) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 977708 + ... + 999621.

It is an arithmetic number, because the mean of its divisors is an integer number (5416895535).

Almost surely, 2^21665593853 is an apocalyptic number.

It is an amenable number.

21665593853 is a deficient number, since it is larger than the sum of its proper divisors (1988287).

21665593853 is a wasteful number, since it uses less digits than its factorization.

21665593853 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1988286.

The product of its digits is 5832000, while the sum is 53.

The spelling of 21665593853 in words is "twenty-one billion, six hundred sixty-five million, five hundred ninety-three thousand, eight hundred fifty-three".