999979999 has 4 divisors (see below), whose sum is σ = 1001808664. Its totient is φ = 998151336.

The previous prime is 999979961. The next prime is 999980011.

999979999 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 999979999 - 2²⁵ = 966425567 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 (999979919) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 913512 + ... + 914605.

It is an arithmetic number, because the mean of its divisors is an integer number (250452166).

Almost surely, 2^999979999 is an apocalyptic number.

999979999 is a deficient number, since it is larger than the sum of its proper divisors (1828665).

999979999 is a wasteful number, since it uses less digits than its factorization.

999979999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1828664.

The product of its digits is 301327047, while the sum is 79.

The square root of 999979999 is about 31622.4603565251. The cubic root of 999979999 is about 999.9933329556.

It can be divided in two parts, 9999 and 79999, that added together give a palindrome (89998).

The spelling of 999979999 in words is "nine hundred ninety-nine million, nine hundred seventy-nine thousand, nine hundred ninety-nine".