18566813 has 2 divisors, whose sum is σ = 18566814. Its totient is φ = 18566812.

The previous prime is 18566803. The next prime is 18566837. The reversal of 18566813 is 31866581.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16337764 + 2229049 = 4042^2 + 1493^2 .

It is an emirp because it is prime and its reverse (31866581) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18566813 - 2¹⁴ = 18550429 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18566803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9283406 + 9283407.

It is an arithmetic number, because the mean of its divisors is an integer number (9283407).

Almost surely, 2^18566813 is an apocalyptic number.

It is an amenable number.

18566813 is a deficient number, since it is larger than the sum of its proper divisors (1).

18566813 is an equidigital number, since it uses as much as digits as its factorization.

18566813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34560, while the sum is 38.

The square root of 18566813 is about 4308.9224871190. The cubic root of 18566813 is about 264.7966304871.

The spelling of 18566813 in words is "eighteen million, five hundred sixty-six thousand, eight hundred thirteen".