8991391920 has 160 divisors (see below), whose sum is σ = 32137800192. Its totient is φ = 2036944896.

The previous prime is 8991391883. The next prime is 8991391943. The reversal of 8991391920 is 291931998.

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 166159 + ... + 213521.

Almost surely, 2^8991391920 is an apocalyptic number.

8991391920 is a gapful number since it is divisible by the number (80) 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 8991391920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16068900096).

8991391920 is an abundant number, since it is smaller than the sum of its proper divisors (23146408272).

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

8991391920 is a wasteful number, since it uses less digits than its factorization.

8991391920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47499 (or 47493 counting only the distinct ones).

The product of its (nonzero) digits is 314928, while the sum is 51.

The square root of 8991391920 is about 94822.9503864966. The cubic root of 8991391920 is about 2079.4204438078.

The spelling of 8991391920 in words is "eight billion, nine hundred ninety-one million, three hundred ninety-one thousand, nine hundred twenty".