18815213 has 4 divisors (see below), whose sum is σ = 19080288. Its totient is φ = 18550140.

The previous prime is 18815207. The next prime is 18815221. The reversal of 18815213 is 31251881.

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: 31251881 = 41 ⋅762241.

It is a cyclic number.

It is not a de Polignac number, because 18815213 - 2⁴ = 18815197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18811213) 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, 132431 + ... + 132572.

It is an arithmetic number, because the mean of its divisors is an integer number (4770072).

Almost surely, 2^18815213 is an apocalyptic number.

It is an amenable number.

18815213 is a deficient number, since it is larger than the sum of its proper divisors (265075).

18815213 is an equidigital number, since it uses as much as digits as its factorization.

18815213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265074.

The product of its digits is 1920, while the sum is 29.

The square root of 18815213 is about 4337.6506313902. The cubic root of 18815213 is about 265.9722821477.

The spelling of 18815213 in words is "eighteen million, eight hundred fifteen thousand, two hundred thirteen".