18921555968 has 144 divisors (see below), whose sum is σ = 45941837760. Its totient is φ = 7630553088.

The previous prime is 18921555941. The next prime is 18921555971. The reversal of 18921555968 is 86955512981.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4140821 + ... + 4145387.

It is an arithmetic number, because the mean of its divisors is an integer number (319040540).

Almost surely, 2^18921555968 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 18921555968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22970918880).

18921555968 is an abundant number, since it is smaller than the sum of its proper divisors (27020281792).

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

18921555968 is an equidigital number, since it uses as much as digits as its factorization.

18921555968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4630 (or 4593 counting only the distinct ones).

The product of its digits is 7776000, while the sum is 59.

The spelling of 18921555968 in words is "eighteen billion, nine hundred twenty-one million, five hundred fifty-five thousand, nine hundred sixty-eight".