20638526813 has 4 divisors (see below), whose sum is σ = 21852557820. Its totient is φ = 19424495808.

The previous prime is 20638526729. The next prime is 20638526833. The reversal of 20638526813 is 31862583602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31862583602 = 2 ⋅15931291801.

It can be written as a sum of positive squares in 2 ways, for example, as 17600532889 + 3037993924 = 132667^2 + 55118^2 .

It is a cyclic number.

It is not a de Polignac number, because 20638526813 - 2²⁶ = 20571417949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20638526833) 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, 607015478 + ... + 607015511.

It is an arithmetic number, because the mean of its divisors is an integer number (5463139455).

Almost surely, 2^20638526813 is an apocalyptic number.

It is an amenable number.

20638526813 is a deficient number, since it is larger than the sum of its proper divisors (1214031007).

20638526813 is a wasteful number, since it uses less digits than its factorization.

20638526813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1214031006.

The product of its (nonzero) digits is 414720, while the sum is 44.

The spelling of 20638526813 in words is "twenty billion, six hundred thirty-eight million, five hundred twenty-six thousand, eight hundred thirteen".