18213809 has 4 divisors (see below), whose sum is σ = 18225780. Its totient is φ = 18201840.

The previous prime is 18213803. The next prime is 18213823. The reversal of 18213809 is 90831281.

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

It can be written as a sum of positive squares in 2 ways, for example, as 14592400 + 3621409 = 3820^2 + 1903^2 .

It is a cyclic number.

It is not a de Polignac number, because 18213809 - 2²⁴ = 1436593 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18213803) 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, 3302 + ... + 6879.

It is an arithmetic number, because the mean of its divisors is an integer number (4556445).

Almost surely, 2^18213809 is an apocalyptic number.

It is an amenable number.

18213809 is a deficient number, since it is larger than the sum of its proper divisors (11971).

18213809 is a wasteful number, since it uses less digits than its factorization.

18213809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11970.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 18213809 is about 4267.7639344275. The cubic root of 18213809 is about 263.1077209123.

The spelling of 18213809 in words is "eighteen million, two hundred thirteen thousand, eight hundred nine".