9009900991 has 16 divisors (see below), whose sum is σ = 11092637248. Its totient is φ = 7126444800.

The previous prime is 9009900959. The next prime is 9009901057. The reversal of 9009900991 is 1990099009.

It is a cyclic number.

It is not a de Polignac number, because 9009900991 - 2⁵ = 9009900959 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9009901991) 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, 308251 + ... + 336211.

It is an arithmetic number, because the mean of its divisors is an integer number (693289828).

Almost surely, 2^9009900991 is an apocalyptic number.

9009900991 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

9009900991 is a deficient number, since it is larger than the sum of its proper divisors (2082736257).

9009900991 is a wasteful number, since it uses less digits than its factorization.

9009900991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31522.

The product of its (nonzero) digits is 59049, while the sum is 46.

The square root of 9009900991 is about 94920.4982656539. The cubic root of 9009900991 is about 2080.8463172596.

The spelling of 9009900991 in words is "nine billion, nine million, nine hundred thousand, nine hundred ninety-one".