991845680 has 80 divisors (see below), whose sum is σ = 2706761280. Its totient is φ = 330863616.

The previous prime is 991845677. The next prime is 991845691. The reversal of 991845680 is 86548199.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3215 + ... + 44654.

It is an arithmetic number, because the mean of its divisors is an integer number (33834516).

Almost surely, 2^991845680 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 991845680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1353380640).

991845680 is an abundant number, since it is smaller than the sum of its proper divisors (1714915600).

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

991845680 is a wasteful number, since it uses less digits than its factorization.

991845680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47926 (or 47920 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 50.

The square root of 991845680 is about 31493.5815683132. The cubic root of 991845680 is about 997.2744715770.

The spelling of 991845680 in words is "nine hundred ninety-one million, eight hundred forty-five thousand, six hundred eighty".