21538164393 has 6 divisors (see below), whose sum is σ = 31110681914. Its totient is φ = 14358776256.

The previous prime is 21538164391. The next prime is 21538164409. The reversal of 21538164393 is 39346183512.

21538164393 is a `hidden beast` number, since 21 + 538 + 1 + 6 + 4 + 3 + 93 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19979257104 + 1558907289 = 141348^2 + 39483^2 .

It is not a de Polignac number, because 21538164393 - 2¹ = 21538164391 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21538164391) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1196564680 + ... + 1196564697.

Almost surely, 2^21538164393 is an apocalyptic number.

It is an amenable number.

21538164393 is a deficient number, since it is larger than the sum of its proper divisors (9572517521).

21538164393 is a wasteful number, since it uses less digits than its factorization.

21538164393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2393129383 (or 2393129380 counting only the distinct ones).

The product of its digits is 466560, while the sum is 45.

The spelling of 21538164393 in words is "twenty-one billion, five hundred thirty-eight million, one hundred sixty-four thousand, three hundred ninety-three".