991928720 has 20 divisors (see below), whose sum is σ = 2306234460. Its totient is φ = 396771456.

The previous prime is 991928677. The next prime is 991928723. The reversal of 991928720 is 27829199.

It is a happy number.

991928720 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 244234384 + 747694336 = 15628^2 + 27344^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (991928723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6199475 + ... + 6199634.

It is an arithmetic number, because the mean of its divisors is an integer number (115311723).

Almost surely, 2^991928720 is an apocalyptic number.

It is an amenable number.

991928720 is an abundant number, since it is smaller than the sum of its proper divisors (1314305740).

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

991928720 is a wasteful number, since it uses less digits than its factorization.

991928720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12399122 (or 12399116 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 47.

The square root of 991928720 is about 31494.8999045877. The cubic root of 991928720 is about 997.3023023047.

The spelling of 991928720 in words is "nine hundred ninety-one million, nine hundred twenty-eight thousand, seven hundred twenty".