18642509 has 2 divisors, whose sum is σ = 18642510. Its totient is φ = 18642508.

The previous prime is 18642493. The next prime is 18642517. The reversal of 18642509 is 90524681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17598025 + 1044484 = 4195^2 + 1022^2 .

It is a cyclic number.

It is not a de Polignac number, because 18642509 - 2⁴ = 18642493 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18642539) 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, 9321254 + 9321255.

It is an arithmetic number, because the mean of its divisors is an integer number (9321255).

Almost surely, 2^18642509 is an apocalyptic number.

It is an amenable number.

18642509 is a deficient number, since it is larger than the sum of its proper divisors (1).

18642509 is an equidigital number, since it uses as much as digits as its factorization.

18642509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 18642509 is about 4317.6971871589. The cubic root of 18642509 is about 265.1559969140.

The spelling of 18642509 in words is "eighteen million, six hundred forty-two thousand, five hundred nine".