1999999999 has 4 divisors (see below), whose sum is σ = 2064516160. Its totient is φ = 1935483840.

The previous prime is 1999999973. The next prime is 2000000011. The reversal of 1999999999 is 9999999991.

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 1999999999 - 2⁷ = 1999999871 is a prime.

It is a fibodiv number, since the Fibonacci-like sequence with seeds 1 and 999999999 contains 1999999999 itself.

It is a Duffinian number.

1999999999 is a modest number, since divided by 99999 gives 19999 as remainder.

It is a plaindrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1999999499) 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, 32258034 + ... + 32258095.

It is an arithmetic number, because the mean of its divisors is an integer number (516129040).

Almost surely, 2^1999999999 is an apocalyptic number.

1999999999 is a deficient number, since it is larger than the sum of its proper divisors (64516161).

1999999999 is an equidigital number, since it uses as much as digits as its factorization.

1999999999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64516160.

The product of its digits is 387420489, while the sum is 82.

The square root of 1999999999 is about 44721.3595388155. The cubic root of 1999999999 is about 1259.9210496849.

It can be divided in two parts, 19 and 99999999, that multiplied together give a palindrome (1899999981).

The spelling of 1999999999 in words is "one billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety-nine".