99999815 has 4 divisors (see below), whose sum is σ = 119999784. Its totient is φ = 79999848.

The previous prime is 99999787. The next prime is 99999821. The reversal of 99999815 is 51899999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 51899999 = 59 ⋅879661.

It is a cyclic number.

It is not a de Polignac number, because 99999815 - 2¹⁴ = 99983431 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9999977 + ... + 9999986.

It is an arithmetic number, because the mean of its divisors is an integer number (29999946).

Almost surely, 2^99999815 is an apocalyptic number.

99999815 is a deficient number, since it is larger than the sum of its proper divisors (19999969).

99999815 is a wasteful number, since it uses less digits than its factorization.

99999815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19999968.

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

The square root of 99999815 is about 9999.9907499957. The cubic root of 99999815 is about 464.1585971298.

The spelling of 99999815 in words is "ninety-nine million, nine hundred ninety-nine thousand, eight hundred fifteen".