991566923 has 4 divisors (see below), whose sum is σ = 991651320. Its totient is φ = 991482528.

The previous prime is 991566913. The next prime is 991566929. The reversal of 991566923 is 329665199.

991566923 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 991566923 - 2⁴ = 991566907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991566929) 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, 21038 + ... + 49251.

It is an arithmetic number, because the mean of its divisors is an integer number (247912830).

Almost surely, 2^991566923 is an apocalyptic number.

991566923 is a deficient number, since it is larger than the sum of its proper divisors (84397).

991566923 is a wasteful number, since it uses less digits than its factorization.

991566923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84396.

The product of its digits is 787320, while the sum is 50.

The square root of 991566923 is about 31489.1556412680. The cubic root of 991566923 is about 997.1810352380.

The spelling of 991566923 in words is "nine hundred ninety-one million, five hundred sixty-six thousand, nine hundred twenty-three".