18931568640 has 208 divisors, whose sum is σ = 63211978368. Its totient is φ = 4828561408.

The previous prime is 18931568627. The next prime is 18931568641. The reversal of 18931568640 is 4686513981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18931568641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1406422 + ... + 1419818.

Almost surely, 2^18931568640 is an apocalyptic number.

18931568640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18931568640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31605989184).

18931568640 is an abundant number, since it is smaller than the sum of its proper divisors (44280409728).

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

18931568640 is a wasteful number, since it uses less digits than its factorization.

18931568640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13452 (or 13430 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 51.

The spelling of 18931568640 in words is "eighteen billion, nine hundred thirty-one million, five hundred sixty-eight thousand, six hundred forty".