999891 has 16 divisors (see below), whose sum is σ = 1533600. Its totient is φ = 643104.

The previous prime is 999883. The next prime is 999907. The reversal of 999891 is 198999.

It is not a de Polignac number, because 999891 - 2³ = 999883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (999091) 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, 145 + ... + 1421.

It is an arithmetic number, because the mean of its divisors is an integer number (95850).

2⁹⁹⁹⁸⁹¹ is an apocalyptic number.

999891 is a deficient number, since it is larger than the sum of its proper divisors (533709).

999891 is a wasteful number, since it uses less digits than its factorization.

999891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1315 (or 1309 counting only the distinct ones).

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

The square root of 999891 is about 999.9454985148. The cubic root of 999891 is about 99.9963665346.

The spelling of 999891 in words is "nine hundred ninety-nine thousand, eight hundred ninety-one".