18728009 has 2 divisors, whose sum is σ = 18728010. Its totient is φ = 18728008.

The previous prime is 18727991. The next prime is 18728023. The reversal of 18728009 is 90082781.

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., 18088009 + 640000 = 4253^2 + 800^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18728009 is a prime.

It is a super-2 number, since 2×18728009² = 701476642208162, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 18728009.

It is not a weakly prime, because it can be changed into another prime (18728069) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9364004 + 9364005.

It is an arithmetic number, because the mean of its divisors is an integer number (9364005).

Almost surely, 2^18728009 is an apocalyptic number.

It is an amenable number.

18728009 is a deficient number, since it is larger than the sum of its proper divisors (1).

18728009 is an equidigital number, since it uses as much as digits as its factorization.

18728009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 18728009 is about 4327.5869719741. The cubic root of 18728009 is about 265.5607397772.

The spelling of 18728009 in words is "eighteen million, seven hundred twenty-eight thousand, nine".