99991605 has 24 divisors (see below), whose sum is σ = 186108192. Its totient is φ = 45710112.

The previous prime is 99991583. The next prime is 99991609. The reversal of 99991605 is 50619999.

It is a happy number.

It is not a de Polignac number, because 99991605 - 2¹⁰ = 99990581 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99991609) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 67287 + ... + 68756.

It is an arithmetic number, because the mean of its divisors is an integer number (7754508).

Almost surely, 2^99991605 is an apocalyptic number.

It is an amenable number.

99991605 is a deficient number, since it is larger than the sum of its proper divisors (86116587).

99991605 is a wasteful number, since it uses less digits than its factorization.

99991605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136065 (or 136058 counting only the distinct ones).

The product of its (nonzero) digits is 196830, while the sum is 48.

The square root of 99991605 is about 9999.5802411901. The cubic root of 99991605 is about 464.1458942850.

The spelling of 99991605 in words is "ninety-nine million, nine hundred ninety-one thousand, six hundred five".