18564661 has 2 divisors, whose sum is σ = 18564662. Its totient is φ = 18564660.

The previous prime is 18564659. The next prime is 18564673. The reversal of 18564661 is 16646581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17690436 + 874225 = 4206^2 + 935^2 .

It is a cyclic number.

It is not a de Polignac number, because 18564661 - 2¹ = 18564659 is a prime.

Together with 18564659, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 18564661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18564631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9282330 + 9282331.

It is an arithmetic number, because the mean of its divisors is an integer number (9282331).

Almost surely, 2^18564661 is an apocalyptic number.

It is an amenable number.

18564661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18564661 is an equidigital number, since it uses as much as digits as its factorization.

18564661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34560, while the sum is 37.

The square root of 18564661 is about 4308.6727654813. The cubic root of 18564661 is about 264.7863996097.

It can be divided in two parts, 185 and 64661, that added together give a palindrome (64846).

The spelling of 18564661 in words is "eighteen million, five hundred sixty-four thousand, six hundred sixty-one".