999840 has 48 divisors (see below), whose sum is σ = 3151008. Its totient is φ = 266496.

The previous prime is 999809. The next prime is 999853. The reversal of 999840 is 48999.

It is a tau number, because it is divible by the number of its divisors (48).

It is a nialpdrome in base 10.

It is an unprimeable number.

999840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 562 + ... + 1521.

It is an arithmetic number, because the mean of its divisors is an integer number (65646).

2⁹⁹⁹⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

999840 is an abundant number, since it is smaller than the sum of its proper divisors (2151168).

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

999840 is a wasteful number, since it uses less digits than its factorization.

999840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2101 (or 2093 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 39.

The square root of 999840 is about 999.9199967997. The cubic root of 999840 is about 99.9946663822.

It can be divided in two parts, 999 and 840, that multiplied together give a triangular number (839160 = T₁₂₉₅).

The spelling of 999840 in words is "nine hundred ninety-nine thousand, eight hundred forty".