99859991 has 40 divisors (see below), whose sum is σ = 134448000. Its totient is φ = 73347120.

The previous prime is 99859979. The next prime is 99859999. The reversal of 99859991 is 19995899.

It is not a de Polignac number, because 99859991 - 2⁶ = 99859927 is a prime.

It is a Smith number, since the sum of its digits (59) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 99859991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99859999) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 501710 + ... + 501908.

It is an arithmetic number, because the mean of its divisors is an integer number (3361200).

Almost surely, 2^99859991 is an apocalyptic number.

99859991 is a deficient number, since it is larger than the sum of its proper divisors (34588009).

99859991 is a wasteful number, since it uses less digits than its factorization.

99859991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 257 (or 236 counting only the distinct ones).

The product of its digits is 2361960, while the sum is 59.

The square root of 99859991 is about 9992.9970979682. The cubic root of 99859991 is about 463.9421607824.

The spelling of 99859991 in words is "ninety-nine million, eight hundred fifty-nine thousand, nine hundred ninety-one".