991091091 has 32 divisors (see below), whose sum is σ = 1459376640. Its totient is φ = 595482624.

The previous prime is 991091081. The next prime is 991091093. The reversal of 991091091 is 190190199.

It is not a de Polignac number, because 991091091 - 2⁷ = 991090963 is a prime.

It is not an unprimeable number, because it can be changed into a prime (991091093) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 251065 + ... + 254981.

It is an arithmetic number, because the mean of its divisors is an integer number (45605520).

Almost surely, 2^991091091 is an apocalyptic number.

991091091 is a deficient number, since it is larger than the sum of its proper divisors (468285549).

991091091 is a wasteful number, since it uses less digits than its factorization.

991091091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4155.

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

The square root of 991091091 is about 31481.5992446381. The cubic root of 991091091 is about 997.0215010184.

The spelling of 991091091 in words is "nine hundred ninety-one million, ninety-one thousand, ninety-one".