989979991 has 32 divisors (see below), whose sum is σ = 1331882496. Its totient is φ = 710640000.

The previous prime is 989979983. The next prime is 989980003. The reversal of 989979991 is 199979989.

It is not a de Polignac number, because 989979991 - 2³ = 989979983 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 989979991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (989979911) 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, 941416 + ... + 942466.

It is an arithmetic number, because the mean of its divisors is an integer number (41621328).

Almost surely, 2^989979991 is an apocalyptic number.

989979991 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

989979991 is a deficient number, since it is larger than the sum of its proper divisors (341902505).

989979991 is a wasteful number, since it uses less digits than its factorization.

989979991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2023.

The product of its digits is 29760696, while the sum is 70.

The square root of 989979991 is about 31463.9474796155. The cubic root of 989979991 is about 996.6487788624.

The spelling of 989979991 in words is "nine hundred eighty-nine million, nine hundred seventy-nine thousand, nine hundred ninety-one".