99999891 has 6 divisors (see below), whose sum is σ = 144444300. Its totient is φ = 66666588.

The previous prime is 99999847. The next prime is 99999931. The reversal of 99999891 is 19899999.

It is not a de Polignac number, because 99999891 - 2⁶ = 99999827 is a prime.

It is not an unprimeable number, because it can be changed into a prime (99999821) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5555541 + ... + 5555558.

It is an arithmetic number, because the mean of its divisors is an integer number (24074050).

Almost surely, 2^99999891 is an apocalyptic number.

99999891 is a deficient number, since it is larger than the sum of its proper divisors (44444409).

99999891 is a wasteful number, since it uses less digits than its factorization.

99999891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11111105 (or 11111102 counting only the distinct ones).

The product of its digits is 4251528, while the sum is 63.

The square root of 99999891 is about 9999.9945499985. The cubic root of 99999891 is about 464.1587147168.

The spelling of 99999891 in words is "ninety-nine million, nine hundred ninety-nine thousand, eight hundred ninety-one".