9991208880 has 120 divisors (see below), whose sum is σ = 33760057968. Its totient is φ = 2647945728.

The previous prime is 9991208837. The next prime is 9991208977. The reversal of 9991208880 is 888021999.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (120).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 74794 + ... + 159926.

Almost surely, 2^9991208880 is an apocalyptic number.

9991208880 is a gapful number since it is divisible by the number (90) 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 9991208880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16880028984).

9991208880 is an abundant number, since it is smaller than the sum of its proper divisors (23768849088).

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

9991208880 is a wasteful number, since it uses less digits than its factorization.

9991208880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85315 (or 85306 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 54.

The square root of 9991208880 is about 99956.0347352775. The cubic root of 9991208880 is about 2153.8031751419.

The spelling of 9991208880 in words is "nine billion, nine hundred ninety-one million, two hundred eight thousand, eight hundred eighty".