18909931 has 2 divisors, whose sum is σ = 18909932. Its totient is φ = 18909930.

The previous prime is 18909929. The next prime is 18909937. The reversal of 18909931 is 13990981.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 18909931 - 2¹ = 18909929 is a prime.

It is a super-2 number, since 2×18909931² = 715170980849522, which contains 22 as substring.

Together with 18909929, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (18909937) 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, 9454965 + 9454966.

It is an arithmetic number, because the mean of its divisors is an integer number (9454966).

Almost surely, 2^18909931 is an apocalyptic number.

18909931 is a deficient number, since it is larger than the sum of its proper divisors (1).

18909931 is an equidigital number, since it uses as much as digits as its factorization.

18909931 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17496, while the sum is 40.

The square root of 18909931 is about 4348.5550473692. Note that the first 3 decimals coincide. The cubic root of 18909931 is about 266.4178472458.

The spelling of 18909931 in words is "eighteen million, nine hundred nine thousand, nine hundred thirty-one".