999864 has 40 divisors (see below), whose sum is σ = 2802360. Its totient is φ = 333072.

The previous prime is 999863. The next prime is 999883. The reversal of 999864 is 468999.

999864 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a nude number because it is divisible by every one of its digits.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999863) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 124 + ... + 1419.

It is an arithmetic number, because the mean of its divisors is an integer number (70059).

2⁹⁹⁹⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 999864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1401180).

999864 is an abundant number, since it is smaller than the sum of its proper divisors (1802496).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

999864 is a wasteful number, since it uses less digits than its factorization.

999864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1561 (or 1548 counting only the distinct ones).

The product of its digits is 139968, while the sum is 45.

The square root of 999864 is about 999.9319976878. The cubic root of 999864 is about 99.9954664611.

The spelling of 999864 in words is "nine hundred ninety-nine thousand, eight hundred sixty-four".