999998999 has 4 divisors (see below), whose sum is σ = 1000672080. Its totient is φ = 999325920.

The previous prime is 999998981. The next prime is 999999001. The reversal of 999998999 is 999899999.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 999998999 - 2¹² = 999994903 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999998929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 334307 + ... + 337284.

It is an arithmetic number, because the mean of its divisors is an integer number (250168020).

Almost surely, 2^999998999 is an apocalyptic number.

999998999 is a deficient number, since it is larger than the sum of its proper divisors (673081).

999998999 is a wasteful number, since it uses less digits than its factorization.

999998999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 673080.

The product of its digits is 344373768, while the sum is 80.

The square root of 999998999 is about 31622.7607744801. The cubic root of 999998999 is about 999.9996663332. Note that the first 3 decimals are identical.

The spelling of 999998999 in words is "nine hundred ninety-nine million, nine hundred ninety-eight thousand, nine hundred ninety-nine".