91009900991 has 16 divisors (see below), whose sum is σ = 99988266240. Its totient is φ = 82452110400.

The previous prime is 91009900987. The next prime is 91009901053. The reversal of 91009900991 is 19900990019.

It is a cyclic number.

It is not a de Polignac number, because 91009900991 - 2² = 91009900987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91009903991) 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, 2072816 + ... + 2116266.

It is an arithmetic number, because the mean of its divisors is an integer number (6249266640).

Almost surely, 2^91009900991 is an apocalyptic number.

91009900991 is a deficient number, since it is larger than the sum of its proper divisors (8978365249).

91009900991 is a wasteful number, since it uses less digits than its factorization.

91009900991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48286.

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

The spelling of 91009900991 in words is "ninety-one billion, nine million, nine hundred thousand, nine hundred ninety-one".