18899991 has 12 divisors (see below), whose sum is σ = 29781960. Its totient is φ = 11454480.

The previous prime is 18899989. The next prime is 18899999. The reversal of 18899991 is 19999881.

It is not a de Polignac number, because 18899991 - 2¹ = 18899989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18899999) 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, 95356 + ... + 95553.

It is an arithmetic number, because the mean of its divisors is an integer number (2481830).

Almost surely, 2^18899991 is an apocalyptic number.

18899991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18899991 is a deficient number, since it is larger than the sum of its proper divisors (10881969).

18899991 is a wasteful number, since it uses less digits than its factorization.

18899991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 190926 (or 190923 counting only the distinct ones).

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

The square root of 18899991 is about 4347.4119887584. The cubic root of 18899991 is about 266.3711582416.

It can be divided in two parts, 18 and 899991, that added together give a palindrome (900009).

The spelling of 18899991 in words is "eighteen million, eight hundred ninety-nine thousand, nine hundred ninety-one".