99611991 has 16 divisors (see below), whose sum is σ = 147756000. Its totient is φ = 66325824.

The previous prime is 99611933. The next prime is 99611999. The reversal of 99611991 is 19911699.

It is not a de Polignac number, because 99611991 - 2¹¹ = 99609943 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99611999) 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, 26565 + ... + 30081.

It is an arithmetic number, because the mean of its divisors is an integer number (9234750).

Almost surely, 2^99611991 is an apocalyptic number.

99611991 is a deficient number, since it is larger than the sum of its proper divisors (48144009).

99611991 is a wasteful number, since it uses less digits than its factorization.

99611991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4575 (or 4569 counting only the distinct ones).

The product of its digits is 39366, while the sum is 45.

The square root of 99611991 is about 9980.5806945288. The cubic root of 99611991 is about 463.5577791629.

The spelling of 99611991 in words is "ninety-nine million, six hundred eleven thousand, nine hundred ninety-one".