18181805 has 4 divisors (see below), whose sum is σ = 21818172. Its totient is φ = 14545440.

The previous prime is 18181783. The next prime is 18181817. The reversal of 18181805 is 50818181.

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 7086244 + 11095561 = 2662^2 + 3331^2 .

It is not a de Polignac number, because 18181805 - 2¹⁰ = 18180781 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, 1818176 + ... + 1818185.

It is an arithmetic number, because the mean of its divisors is an integer number (5454543).

Almost surely, 2^18181805 is an apocalyptic number.

It is an amenable number.

18181805 is a deficient number, since it is larger than the sum of its proper divisors (3636367).

18181805 is an equidigital number, since it uses as much as digits as its factorization.

18181805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3636366.

The product of its (nonzero) digits is 2560, while the sum is 32.

The square root of 18181805 is about 4264.0127814067. The cubic root of 18181805 is about 262.9535258858.

Adding to 18181805 its reverse (50818181), we get a palindrome (68999986).

The spelling of 18181805 in words is "eighteen million, one hundred eighty-one thousand, eight hundred five".