989581991 has 4 divisors (see below), whose sum is σ = 997136184. Its totient is φ = 982027800.

The previous prime is 989581987. The next prime is 989582003. The reversal of 989581991 is 199185989.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 989581991 - 2² = 989581987 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 989581991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (989581961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3776900 + ... + 3777161.

It is an arithmetic number, because the mean of its divisors is an integer number (249284046).

Almost surely, 2^989581991 is an apocalyptic number.

989581991 is a deficient number, since it is larger than the sum of its proper divisors (7554193).

989581991 is a wasteful number, since it uses less digits than its factorization.

989581991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7554192.

The product of its digits is 2099520, while the sum is 59.

The square root of 989581991 is about 31457.6221447203. The cubic root of 989581991 is about 996.5152006128.

The spelling of 989581991 in words is "nine hundred eighty-nine million, five hundred eighty-one thousand, nine hundred ninety-one".