18991284 has 96 divisors (see below), whose sum is σ = 51179520. Its totient is φ = 5436288.

The previous prime is 18991283. The next prime is 18991303. The reversal of 18991284 is 48219981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18991283) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 240357 + ... + 240435.

It is an arithmetic number, because the mean of its divisors is an integer number (533120).

Almost surely, 2^18991284 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 18991284, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25589760).

18991284 is an abundant number, since it is smaller than the sum of its proper divisors (32188236).

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

18991284 is a wasteful number, since it uses less digits than its factorization.

18991284 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189 (or 187 counting only the distinct ones).

The product of its digits is 41472, while the sum is 42.

The square root of 18991284 is about 4357.8990350856. The cubic root of 18991284 is about 266.7993554931.

The spelling of 18991284 in words is "eighteen million, nine hundred ninety-one thousand, two hundred eighty-four".