9991009091 has 4 divisors (see below), whose sum is σ = 11418296112. Its totient is φ = 8563722072.

The previous prime is 9991009069. The next prime is 9991009097. The reversal of 9991009091 is 1909001999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1909001999 = 113 ⋅16893823.

It is a cyclic number.

It is not a de Polignac number, because 9991009091 - 2¹⁴ = 9990992707 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9991009097) 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, 713643500 + ... + 713643513.

It is an arithmetic number, because the mean of its divisors is an integer number (2854574028).

Almost surely, 2^9991009091 is an apocalyptic number.

9991009091 is a deficient number, since it is larger than the sum of its proper divisors (1427287021).

9991009091 is a wasteful number, since it uses less digits than its factorization.

9991009091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1427287020.

The product of its (nonzero) digits is 59049, while the sum is 47.

The square root of 9991009091 is about 99955.0353458994. The cubic root of 9991009091 is about 2153.7888188861.

The spelling of 9991009091 in words is "nine billion, nine hundred ninety-one million, nine thousand, ninety-one".