18509891 has 2 divisors, whose sum is σ = 18509892. Its totient is φ = 18509890.

The previous prime is 18509873. The next prime is 18509899. The reversal of 18509891 is 19890581.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18509891 - 2¹⁴ = 18493507 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18509899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9254945 + 9254946.

It is an arithmetic number, because the mean of its divisors is an integer number (9254946).

Almost surely, 2^18509891 is an apocalyptic number.

18509891 is a deficient number, since it is larger than the sum of its proper divisors (1).

18509891 is an equidigital number, since it uses as much as digits as its factorization.

18509891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 41.

The square root of 18509891 is about 4302.3122852717. The cubic root of 18509891 is about 264.5257496167.

The spelling of 18509891 in words is "eighteen million, five hundred nine thousand, eight hundred ninety-one".