991009911 has 4 divisors (see below), whose sum is σ = 1321346552. Its totient is φ = 660673272.

The previous prime is 991009907. The next prime is 991009939. The reversal of 991009911 is 119900199.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 991009911 - 2² = 991009907 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991009911.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991009991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 165168316 + ... + 165168321.

It is an arithmetic number, because the mean of its divisors is an integer number (330336638).

Almost surely, 2^991009911 is an apocalyptic number.

991009911 is a deficient number, since it is larger than the sum of its proper divisors (330336641).

991009911 is a wasteful number, since it uses less digits than its factorization.

991009911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330336640.

The product of its (nonzero) digits is 6561, while the sum is 39.

The square root of 991009911 is about 31480.3098936462. The cubic root of 991009911 is about 996.9942783557.

The spelling of 991009911 in words is "nine hundred ninety-one million, nine thousand, nine hundred eleven".