1999781988 has 12 divisors (see below), whose sum is σ = 4666158000. Its totient is φ = 666593992.

The previous prime is 1999781983. The next prime is 1999782047. The reversal of 1999781988 is 8891879991.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (1999781983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83324238 + ... + 83324261.

It is an arithmetic number, because the mean of its divisors is an integer number (388846500).

Almost surely, 2^1999781988 is an apocalyptic number.

It is an amenable number.

1999781988 is an abundant number, since it is smaller than the sum of its proper divisors (2666376012).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1999781988 is a wasteful number, since it uses less digits than its factorization.

1999781988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 166648506 (or 166648504 counting only the distinct ones).

The product of its digits is 23514624, while the sum is 69.

The square root of 1999781988 is about 44718.9220353085. The cubic root of 1999781988 is about 1259.8752685800.

The spelling of 1999781988 in words is "one billion, nine hundred ninety-nine million, seven hundred eighty-one thousand, nine hundred eighty-eight".