991589009 has 4 divisors (see below), whose sum is σ = 1000856304. Its totient is φ = 982321716.

The previous prime is 991588993. The next prime is 991589017. The reversal of 991589009 is 900985199.

991589009 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 Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 900985199 = 73 ⋅12342263.

It is a cyclic number.

It is not a de Polignac number, because 991589009 - 2⁴ = 991588993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991589029) 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, 4633487 + ... + 4633700.

It is an arithmetic number, because the mean of its divisors is an integer number (250214076).

Almost surely, 2^991589009 is an apocalyptic number.

It is an amenable number.

991589009 is a deficient number, since it is larger than the sum of its proper divisors (9267295).

991589009 is a wasteful number, since it uses less digits than its factorization.

991589009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9267294.

The product of its (nonzero) digits is 262440, while the sum is 50.

The square root of 991589009 is about 31489.5063314749. The cubic root of 991589009 is about 997.1884388657.

The spelling of 991589009 in words is "nine hundred ninety-one million, five hundred eighty-nine thousand, nine".