999999 has 64 divisors (see below), whose sum is σ = 2042880. Its totient is φ = 466560.

The previous prime is 999983. The next prime is 1000003.

999999 is nontrivially palindromic in base 10.

It is a Cunningham number, because it is equal to 10⁶-1.

It is a trimorphic number since its cube, 999997000002999999, ends in 999999.

It is not a de Polignac number, because 999999 - 2⁴ = 999983 is a prime.

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

999999 is a modest number, since divided by 9999 gives 99 as remainder.

999999 is a nontrivial repdigit in base 10.

It is a plaindrome in base 5 and base 10.

It is a nialpdrome in base 10.

It is a zygodrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999959) by changing a digit.

It is a Kaprekar number, because its square (999998000001) can be partitioned into two parts whose sum is 999999.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 27009 + ... + 27045.

It is an arithmetic number, because the mean of its divisors is an integer number (31920).

2⁹⁹⁹⁹⁹⁹ is an apocalyptic number.

999999 is a gapful number since it is divisible by the number (99) formed by its first and last digit.

999999 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

999999 is a wasteful number, since it uses less digits than its factorization.

999999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77 (or 71 counting only the distinct ones).

The product of its digits is 531441, while the sum is 54.

The square root of 999999 is about 999.9994999999. Note that the first 3 decimals coincide. The cubic root of 999999 is about 99.9999666667. Note that the first 4 decimals are identical.

The spelling of 999999 in words is "nine hundred ninety-nine thousand, nine hundred ninety-nine".