18942809 has 2 divisors, whose sum is σ = 18942810. Its totient is φ = 18942808.

The previous prime is 18942769. The next prime is 18942851. The reversal of 18942809 is 90824981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16974400 + 1968409 = 4120^2 + 1403^2 .

It is a cyclic number.

It is not a de Polignac number, because 18942809 - 2²⁴ = 2165593 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18942899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9471404 + 9471405.

It is an arithmetic number, because the mean of its divisors is an integer number (9471405).

Almost surely, 2^18942809 is an apocalyptic number.

It is an amenable number.

18942809 is a deficient number, since it is larger than the sum of its proper divisors (1).

18942809 is an equidigital number, since it uses as much as digits as its factorization.

18942809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 41472, while the sum is 41.

The square root of 18942809 is about 4352.3337417988. Note that the first 3 decimals coincide. The cubic root of 18942809 is about 266.5721614771.

The spelling of 18942809 in words is "eighteen million, nine hundred forty-two thousand, eight hundred nine".