991091001 has 16 divisors (see below), whose sum is σ = 1355031104. Its totient is φ = 644143104.

The previous prime is 991090967. The next prime is 991091009. The reversal of 991091001 is 100190199.

It is not a de Polignac number, because 991091001 - 2⁹ = 991090489 is a prime.

It is a super-2 number, since 2×991091001² = 1964522744526364002, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 991091001.

It is not an unprimeable number, because it can be changed into a prime (991091009) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5920 + ... + 44913.

It is an arithmetic number, because the mean of its divisors is an integer number (84689444).

Almost surely, 2^991091001 is an apocalyptic number.

It is an amenable number.

991091001 is a deficient number, since it is larger than the sum of its proper divisors (363940103).

991091001 is a wasteful number, since it uses less digits than its factorization.

991091001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51000.

The product of its (nonzero) digits is 729, while the sum is 30.

The square root of 991091001 is about 31481.5978152317. The cubic root of 991091001 is about 997.0214708388.

The spelling of 991091001 in words is "nine hundred ninety-one million, ninety-one thousand, one".