999919999 has 4 divisors (see below), whose sum is σ = 1076836936. Its totient is φ = 923003064.

The previous prime is 999919981. The next prime is 999920003.

It is a happy number.

999919999 is nontrivially palindromic in base 10.

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 999919999 - 2²⁵ = 966365567 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 (999919919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38458449 + ... + 38458474.

It is an arithmetic number, because the mean of its divisors is an integer number (269209234).

Almost surely, 2^999919999 is an apocalyptic number.

999919999 is a deficient number, since it is larger than the sum of its proper divisors (76916937).

999919999 is a wasteful number, since it uses less digits than its factorization.

999919999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76916936.

The product of its digits is 43046721, while the sum is 73.

The square root of 999919999 is about 31621.5116495085. The cubic root of 999919999 is about 999.9733322888.

It can be divided in two parts, 9999 and 19999, that multiplied together give a triangular number (199970001 = T₁₉₉₉₈).

The spelling of 999919999 in words is "nine hundred ninety-nine million, nine hundred nineteen thousand, nine hundred ninety-nine".