1991899 has 24 divisors (see below), whose sum is σ = 2585520. Its totient is φ = 1520064.

The previous prime is 1991893. The next prime is 1991911. The reversal of 1991899 is 9981991.

It is not a de Polignac number, because 1991899 - 2⁹ = 1991387 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33732 + ... + 33790.

It is an arithmetic number, because the mean of its divisors is an integer number (107730).

2^1991899 is an apocalyptic number.

1991899 is a deficient number, since it is larger than the sum of its proper divisors (593621).

1991899 is a wasteful number, since it uses less digits than its factorization.

1991899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139 (or 132 counting only the distinct ones).

The product of its digits is 52488, while the sum is 46.

The square root of 1991899 is about 1411.3465201714. The cubic root of 1991899 is about 125.8217644535.

The spelling of 1991899 in words is "one million, nine hundred ninety-one thousand, eight hundred ninety-nine".