1999779988 has 24 divisors (see below), whose sum is σ = 3655314432. Its totient is φ = 955488864.

The previous prime is 1999779967. The next prime is 1999780037. The reversal of 1999779988 is 8899779991.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 90006 + ... + 110002.

It is an arithmetic number, because the mean of its divisors is an integer number (152304768).

Almost surely, 2^1999779988 is an apocalyptic number.

It is an amenable number.

1999779988 is a deficient number, since it is larger than the sum of its proper divisors (1655534444).

1999779988 is a wasteful number, since it uses less digits than its factorization.

1999779988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21111 (or 21109 counting only the distinct ones).

The product of its digits is 185177664, while the sum is 76.

The square root of 1999779988 is about 44718.8996734043. The cubic root of 1999779988 is about 1259.8748485757.

It can be divided in two parts, 19997 and 79988, that multiplied together give a square (1599520036 = 39994²).

The spelling of 1999779988 in words is "one billion, nine hundred ninety-nine million, seven hundred seventy-nine thousand, nine hundred eighty-eight".