18731638639 has 4 divisors (see below), whose sum is σ = 21407587024. Its totient is φ = 16055690256.

The previous prime is 18731638631. The next prime is 18731638697. The reversal of 18731638639 is 93683613781.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18731638639 - 2³ = 18731638631 is a prime.

It is a super-3 number, since 3×18731638639³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18731638639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18731638631) 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, 1337974182 + ... + 1337974195.

It is an arithmetic number, because the mean of its divisors is an integer number (5351896756).

Almost surely, 2^18731638639 is an apocalyptic number.

18731638639 is a deficient number, since it is larger than the sum of its proper divisors (2675948385).

18731638639 is an equidigital number, since it uses as much as digits as its factorization.

18731638639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2675948384.

The product of its digits is 3919104, while the sum is 55.

The spelling of 18731638639 in words is "eighteen billion, seven hundred thirty-one million, six hundred thirty-eight thousand, six hundred thirty-nine".