18991984 has 60 divisors (see below), whose sum is σ = 42218280. Its totient is φ = 8198400.

The previous prime is 18991981. The next prime is 18992027. The reversal of 18991984 is 48919981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18991981) 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 in 11 ways as a sum of consecutive naturals, for example, 311314 + ... + 311374.

It is an arithmetic number, because the mean of its divisors is an integer number (703638).

Almost surely, 2^18991984 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18991984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21109140).

18991984 is an abundant number, since it is smaller than the sum of its proper divisors (23226296).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18991984 is a wasteful number, since it uses less digits than its factorization.

18991984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170 (or 103 counting only the distinct ones).

The product of its digits is 186624, while the sum is 49.

The square root of 18991984 is about 4357.9793482760. The cubic root of 18991984 is about 266.8026334399.

It can be divided in two parts, 1899 and 1984, that added together give a palindrome (3883).

The spelling of 18991984 in words is "eighteen million, nine hundred ninety-one thousand, nine hundred eighty-four".