18605581 has 2 divisors, whose sum is σ = 18605582. Its totient is φ = 18605580.

The previous prime is 18605569. The next prime is 18605623. The reversal of 18605581 is 18550681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16892100 + 1713481 = 4110^2 + 1309^2 .

It is an emirp because it is prime and its reverse (18550681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18605581 - 2⁷ = 18605453 is a prime.

It is a super-2 number, since 2×18605581² = 692335288695122, which contains 22 as substring.

It is equal to p_1187494 and since 18605581 and 1187494 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18605281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9302790 + 9302791.

It is an arithmetic number, because the mean of its divisors is an integer number (9302791).

Almost surely, 2^18605581 is an apocalyptic number.

It is an amenable number.

18605581 is a deficient number, since it is larger than the sum of its proper divisors (1).

18605581 is an equidigital number, since it uses as much as digits as its factorization.

18605581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9600, while the sum is 34.

The square root of 18605581 is about 4313.4187137351. The cubic root of 18605581 is about 264.9808031662.

The spelling of 18605581 in words is "eighteen million, six hundred five thousand, five hundred eighty-one".