18809891 has 2 divisors, whose sum is σ = 18809892. Its totient is φ = 18809890.

The previous prime is 18809887. The next prime is 18809941. The reversal of 18809891 is 19890881.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (19890881) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18809891 - 2² = 18809887 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18809881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9404945 + 9404946.

It is an arithmetic number, because the mean of its divisors is an integer number (9404946).

Almost surely, 2^18809891 is an apocalyptic number.

18809891 is a deficient number, since it is larger than the sum of its proper divisors (1).

18809891 is an equidigital number, since it uses as much as digits as its factorization.

18809891 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 44.

The square root of 18809891 is about 4337.0371222760. The cubic root of 18809891 is about 265.9472024783.

The spelling of 18809891 in words is "eighteen million, eight hundred nine thousand, eight hundred ninety-one".