991899 has 16 divisors (see below), whose sum is σ = 1556640. Its totient is φ = 622080.

The previous prime is 991889. The next prime is 991901. The reversal of 991899 is 998199.

It is not a de Polignac number, because 991899 - 2⁴ = 991883 is a prime.

Its product of digits (52488) is a multiple of the sum of its prime factors (2187).

It is not an unprimeable number, because it can be changed into a prime (991889) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 622 + ... + 1539.

It is an arithmetic number, because the mean of its divisors is an integer number (97290).

2⁹⁹¹⁸⁹⁹ is an apocalyptic number.

991899 is a deficient number, since it is larger than the sum of its proper divisors (564741).

991899 is a wasteful number, since it uses less digits than its factorization.

991899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2187 (or 2181 counting only the distinct ones).

The product of its digits is 52488, while the sum is 45.

The square root of 991899 is about 995.9412633283. The cubic root of 991899 is about 99.7292341871.

The spelling of 991899 in words is "nine hundred ninety-one thousand, eight hundred ninety-nine".