1998888991 has 32 divisors (see below), whose sum is σ = 2349139968. Its totient is φ = 1682672640.

The previous prime is 1998888943. The next prime is 1998889033.

1998888991 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1998888991 - 2¹⁷ = 1998757919 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 1998888991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1998888911) 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, 1152561 + ... + 1154293.

It is an arithmetic number, because the mean of its divisors is an integer number (73410624).

Almost surely, 2^1998888991 is an apocalyptic number.

1998888991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1998888991 is a deficient number, since it is larger than the sum of its proper divisors (350250977).

1998888991 is a wasteful number, since it uses less digits than its factorization.

1998888991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1911.

The product of its digits is 26873856, while the sum is 70.

The square root of 1998888991 is about 44708.9363662344. The cubic root of 1998888991 is about 1259.6877094114.

The spelling of 1998888991 in words is "one billion, nine hundred ninety-eight million, eight hundred eighty-eight thousand, nine hundred ninety-one".