18661009 has 2 divisors, whose sum is σ = 18661010. Its totient is φ = 18661008.

The previous prime is 18660959. The next prime is 18661043. The reversal of 18661009 is 90016681.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9828225 + 8832784 = 3135^2 + 2972^2 .

It is an emirp because it is prime and its reverse (90016681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18661009 - 2¹⁷ = 18529937 is a prime.

It is not a weakly prime, because it can be changed into another prime (18661079) 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, 9330504 + 9330505.

It is an arithmetic number, because the mean of its divisors is an integer number (9330505).

Almost surely, 2^18661009 is an apocalyptic number.

It is an amenable number.

18661009 is a deficient number, since it is larger than the sum of its proper divisors (1).

18661009 is an equidigital number, since it uses as much as digits as its factorization.

18661009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 18661009 is about 4319.8390016296. The cubic root of 18661009 is about 265.2436776049.

The spelling of 18661009 in words is "eighteen million, six hundred sixty-one thousand, nine".