18218213 has 4 divisors (see below), whose sum is σ = 19619628. Its totient is φ = 16816800.

The previous prime is 18218209. The next prime is 18218257. The reversal of 18218213 is 31281281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31281281 = 227 ⋅137803.

It can be written as a sum of positive squares in 2 ways, for example, as 5841889 + 12376324 = 2417^2 + 3518^2 .

It is not a de Polignac number, because 18218213 - 2² = 18218209 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 (18218413) 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, 700688 + ... + 700713.

It is an arithmetic number, because the mean of its divisors is an integer number (4904907).

Almost surely, 2^18218213 is an apocalyptic number.

18218213 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

18218213 is a deficient number, since it is larger than the sum of its proper divisors (1401415).

18218213 is a wasteful number, since it uses less digits than its factorization.

18218213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1401414.

The product of its digits is 768, while the sum is 26.

The square root of 18218213 is about 4268.2798643013. The cubic root of 18218213 is about 263.1289252089.

Adding to 18218213 its reverse (31281281), we get a palindrome (49499494).

The spelling of 18218213 in words is "eighteen million, two hundred eighteen thousand, two hundred thirteen".