99815 has 4 divisors (see below), whose sum is σ = 119784. Its totient is φ = 79848.

The previous prime is 99809. The next prime is 99817. The reversal of 99815 is 51899.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 99815 - 2⁸ = 99559 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99817) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9977 + ... + 9986.

It is an arithmetic number, because the mean of its divisors is an integer number (29946).

2⁹⁹⁸¹⁵ is an apocalyptic number.

99815 is a deficient number, since it is larger than the sum of its proper divisors (19969).

99815 is a wasteful number, since it uses less digits than its factorization.

99815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19968.

The product of its digits is 3240, while the sum is 32.

The square root of 99815 is about 315.9351199218. The cubic root of 99815 is about 46.3872475359.

The spelling of 99815 in words is "ninety-nine thousand, eight hundred fifteen".