1999949991 has 8 divisors (see below), whose sum is σ = 2871723120. Its totient is φ = 1230738432.

The previous prime is 1999949957. The next prime is 1999950037. The reversal of 1999949991 is 1999499991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1999949991 - 2²¹ = 1997852839 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1999949911) 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 7 ways as a sum of consecutive naturals, for example, 25640346 + ... + 25640423.

It is an arithmetic number, because the mean of its divisors is an integer number (358965390).

Almost surely, 2^1999949991 is an apocalyptic number.

1999949991 is a deficient number, since it is larger than the sum of its proper divisors (871773129).

1999949991 is a wasteful number, since it uses less digits than its factorization.

1999949991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51280785.

The product of its digits is 19131876, while the sum is 69.

The square root of 1999949991 is about 44720.8004288832. The cubic root of 1999949991 is about 1259.9105485754.

The spelling of 1999949991 in words is "one billion, nine hundred ninety-nine million, nine hundred forty-nine thousand, nine hundred ninety-one".