18211205 has 4 divisors (see below), whose sum is σ = 21853452. Its totient is φ = 14568960.

The previous prime is 18211201. The next prime is 18211213. The reversal of 18211205 is 50211281.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50211281 = 19 ⋅2642699.

It can be written as a sum of positive squares in 2 ways, for example, as 3265249 + 14945956 = 1807^2 + 3866^2 .

It is not a de Polignac number, because 18211205 - 2² = 18211201 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 (18211201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1821116 + ... + 1821125.

It is an arithmetic number, because the mean of its divisors is an integer number (5463363).

Almost surely, 2^18211205 is an apocalyptic number.

It is an amenable number.

18211205 is a deficient number, since it is larger than the sum of its proper divisors (3642247).

18211205 is an equidigital number, since it uses as much as digits as its factorization.

18211205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3642246.

The product of its (nonzero) digits is 160, while the sum is 20.

The square root of 18211205 is about 4267.4588457301. The cubic root of 18211205 is about 263.0951816139.

Adding to 18211205 its reverse (50211281), we get a palindrome (68422486).

The spelling of 18211205 in words is "eighteen million, two hundred eleven thousand, two hundred five".