18908891 has 2 divisors, whose sum is σ = 18908892. Its totient is φ = 18908890.

The previous prime is 18908881. The next prime is 18908893. The reversal of 18908891 is 19880981.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (19880981) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 16880681 and 18608861.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18908891 is a prime.

Together with 18908893, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18908893) 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, 9454445 + 9454446.

It is an arithmetic number, because the mean of its divisors is an integer number (9454446).

Almost surely, 2^18908891 is an apocalyptic number.

18908891 is a deficient number, since it is larger than the sum of its proper divisors (1).

18908891 is an equidigital number, since it uses as much as digits as its factorization.

18908891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 41472, while the sum is 44.

The square root of 18908891 is about 4348.4354657739. The cubic root of 18908891 is about 266.4129630461.

The spelling of 18908891 in words is "eighteen million, nine hundred eight thousand, eight hundred ninety-one".