991888165 has 4 divisors (see below), whose sum is σ = 1190265804. Its totient is φ = 793510528.

The previous prime is 991888153. The next prime is 991888199. The reversal of 991888165 is 561888199.

991888165 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 an emirpimes, since its reverse is a distinct semiprime: 561888199 = 17 ⋅33052247.

It can be written as a sum of positive squares in 2 ways, for example, as 360924004 + 630964161 = 18998^2 + 25119^2 .

It is a cyclic number.

It is not a de Polignac number, because 991888165 - 2²⁹ = 455017253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99188812 + ... + 99188821.

It is an arithmetic number, because the mean of its divisors is an integer number (297566451).

Almost surely, 2^991888165 is an apocalyptic number.

It is an amenable number.

991888165 is a deficient number, since it is larger than the sum of its proper divisors (198377639).

991888165 is a wasteful number, since it uses less digits than its factorization.

991888165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198377638.

The product of its digits is 1244160, while the sum is 55.

The square root of 991888165 is about 31494.2560636063. The cubic root of 991888165 is about 997.2887105532.

The spelling of 991888165 in words is "nine hundred ninety-one million, eight hundred eighty-eight thousand, one hundred sixty-five".