991521804 has 96 divisors (see below), whose sum is σ = 3015000576. Its totient is φ = 246113280.

The previous prime is 991521799. The next prime is 991521829. The reversal of 991521804 is 408125199.

It is a Harshad number since it is a multiple of its sum of digits (39).

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, 8142 + ... + 45269.

It is an arithmetic number, because the mean of its divisors is an integer number (31406256).

Almost surely, 2^991521804 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 991521804, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1507500288).

991521804 is an abundant number, since it is smaller than the sum of its proper divisors (2023478772).

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

991521804 is a wasteful number, since it uses less digits than its factorization.

991521804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53455 (or 53453 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 39.

The square root of 991521804 is about 31488.4392118758. The cubic root of 991521804 is about 997.1659101895.

The spelling of 991521804 in words is "nine hundred ninety-one million, five hundred twenty-one thousand, eight hundred four".