18581813 has 2 divisors, whose sum is σ = 18581814. Its totient is φ = 18581812.

The previous prime is 18581777. The next prime is 18581819. The reversal of 18581813 is 31818581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15547249 + 3034564 = 3943^2 + 1742^2 .

It is a cyclic number.

It is not a de Polignac number, because 18581813 - 2⁶ = 18581749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18581819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9290906 + 9290907.

It is an arithmetic number, because the mean of its divisors is an integer number (9290907).

Almost surely, 2^18581813 is an apocalyptic number.

It is an amenable number.

18581813 is a deficient number, since it is larger than the sum of its proper divisors (1).

18581813 is an equidigital number, since it uses as much as digits as its factorization.

18581813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7680, while the sum is 35.

The square root of 18581813 is about 4310.6627100714. The cubic root of 18581813 is about 264.8679204154.

The spelling of 18581813 in words is "eighteen million, five hundred eighty-one thousand, eight hundred thirteen".