18705809 has 2 divisors, whose sum is σ = 18705810. Its totient is φ = 18705808.

The previous prime is 18705787. The next prime is 18705821. The reversal of 18705809 is 90850781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9985600 + 8720209 = 3160^2 + 2953^2 .

It is a cyclic number.

It is not a de Polignac number, because 18705809 - 2¹² = 18701713 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18705409) 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, 9352904 + 9352905.

It is an arithmetic number, because the mean of its divisors is an integer number (9352905).

Almost surely, 2^18705809 is an apocalyptic number.

It is an amenable number.

18705809 is a deficient number, since it is larger than the sum of its proper divisors (1).

18705809 is an equidigital number, since it uses as much as digits as its factorization.

18705809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20160, while the sum is 38.

The square root of 18705809 is about 4325.0212716240. The cubic root of 18705809 is about 265.4557672477.

The spelling of 18705809 in words is "eighteen million, seven hundred five thousand, eight hundred nine".