78021889664 has 64 divisors (see below), whose sum is σ = 156894645600. Its totient is φ = 38645468160.

The previous prime is 78021889643. The next prime is 78021889667. The reversal of 78021889664 is 46698812087.

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (78021889667) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10375634 + ... + 10383150.

Almost surely, 2^78021889664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 78021889664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (78447322800).

78021889664 is an abundant number, since it is smaller than the sum of its proper divisors (78872755936).

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

78021889664 is a wasteful number, since it uses less digits than its factorization.

78021889664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8281 (or 8269 counting only the distinct ones).

The product of its (nonzero) digits is 9289728, while the sum is 59.

The spelling of 78021889664 in words is "seventy-eight billion, twenty-one million, eight hundred eighty-nine thousand, six hundred sixty-four".