899991 has 20 divisors (see below), whose sum is σ = 1382304. Its totient is φ = 583200.

The previous prime is 899981. The next prime is 900001. The reversal of 899991 is 199998.

It is an interprime number because it is at equal distance from previous prime (899981) and next prime (900001).

It is not a de Polignac number, because 899991 - 2⁷ = 899863 is a prime.

Its product of digits (52488) is a multiple of the sum of its prime factors (324).

It is a nialpdrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (899971) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3186 + ... + 3456.

2⁸⁹⁹⁹⁹¹ is an apocalyptic number.

899991 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

899991 is a deficient number, since it is larger than the sum of its proper divisors (482313).

899991 is a wasteful number, since it uses less digits than its factorization.

899991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324 (or 315 counting only the distinct ones).

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

The square root of 899991 is about 948.6785546222. The cubic root of 899991 is about 96.5486166297.

It can be divided in two parts, 89999 and 1, that added together give a square (90000 = 300²).

The spelling of 899991 in words is "eight hundred ninety-nine thousand, nine hundred ninety-one".