18643312644 has 36 divisors (see below), whose sum is σ = 47815221552. Its totient is φ = 5649488240.

The previous prime is 18643312643. The next prime is 18643312691. The reversal of 18643312644 is 44621334681.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 18643312596 and 18643312605.

It is not an unprimeable number, because it can be changed into a prime (18643312643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6418422 + ... + 6421325.

Almost surely, 2^18643312644 is an apocalyptic number.

It is an amenable number.

18643312644 is an abundant number, since it is smaller than the sum of its proper divisors (29171908908).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18643312644 is a wasteful number, since it uses less digits than its factorization.

18643312644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12839776 (or 12839763 counting only the distinct ones).

The product of its digits is 331776, while the sum is 42.

The spelling of 18643312644 in words is "eighteen billion, six hundred forty-three million, three hundred twelve thousand, six hundred forty-four".