18989991 has 16 divisors (see below), whose sum is σ = 28895200. Its totient is φ = 12317184.

The previous prime is 18989959. The next prime is 18990017. The reversal of 18989991 is 19998981.

It is not a de Polignac number, because 18989991 - 2⁵ = 18989959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18989291) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8506 + ... + 10503.

It is an arithmetic number, because the mean of its divisors is an integer number (1805950).

Almost surely, 2^18989991 is an apocalyptic number.

18989991 is a deficient number, since it is larger than the sum of its proper divisors (9905209).

18989991 is a wasteful number, since it uses less digits than its factorization.

18989991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19055 (or 19049 counting only the distinct ones).

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

The square root of 18989991 is about 4357.7506812575. The cubic root of 18989991 is about 266.7933004453.

The spelling of 18989991 in words is "eighteen million, nine hundred eighty-nine thousand, nine hundred ninety-one".