18399813 has 4 divisors (see below), whose sum is σ = 24533088. Its totient is φ = 12266540.

The previous prime is 18399791. The next prime is 18399853. The reversal of 18399813 is 31899381.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 31899381 = 3 ⋅10633127.

It is a cyclic number.

It is not a de Polignac number, because 18399813 - 2⁵ = 18399781 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18399853) 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, 3066633 + ... + 3066638.

It is an arithmetic number, because the mean of its divisors is an integer number (6133272).

Almost surely, 2^18399813 is an apocalyptic number.

It is an amenable number.

18399813 is a deficient number, since it is larger than the sum of its proper divisors (6133275).

18399813 is an equidigital number, since it uses as much as digits as its factorization.

18399813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6133274.

The product of its digits is 46656, while the sum is 42.

The square root of 18399813 is about 4289.5003205502. The cubic root of 18399813 is about 264.0003300042. Note that the first 3 decimals are identical.

The spelling of 18399813 in words is "eighteen million, three hundred ninety-nine thousand, eight hundred thirteen".