18999891 has 12 divisors (see below), whose sum is σ = 28028832. Its totient is φ = 12396816.

The previous prime is 18999889. The next prime is 18999913. The reversal of 18999891 is 19899981.

It is not a de Polignac number, because 18999891 - 2¹ = 18999889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18999821) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22036 + ... + 22881.

It is an arithmetic number, because the mean of its divisors is an integer number (2335736).

Almost surely, 2^18999891 is an apocalyptic number.

18999891 is a deficient number, since it is larger than the sum of its proper divisors (9028941).

18999891 is a wasteful number, since it uses less digits than its factorization.

18999891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44970 (or 44967 counting only the distinct ones).

The product of its digits is 419904, while the sum is 54.

The square root of 18999891 is about 4358.8864403652. The cubic root of 18999891 is about 266.8396545979.

The spelling of 18999891 in words is "eighteen million, nine hundred ninety-nine thousand, eight hundred ninety-one".