189991008 has 144 divisors (see below), whose sum is σ = 572107536. Its totient is φ = 62000640.

The previous prime is 189991001. The next prime is 189991037. The reversal of 189991008 is 800199981.

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (189991001) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 411898 + ... + 412358.

It is an arithmetic number, because the mean of its divisors is an integer number (3972969).

Almost surely, 2^189991008 is an apocalyptic number.

189991008 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 189991008, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (286053768).

189991008 is an abundant number, since it is smaller than the sum of its proper divisors (382116528).

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

189991008 is an equidigital number, since it uses as much as digits as its factorization.

189991008 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 539 (or 519 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 45.

The square root of 189991008 is about 13783.7225741089. The cubic root of 189991008 is about 574.8806386141.

The spelling of 189991008 in words is "one hundred eighty-nine million, nine hundred ninety-one thousand, eight".