1999079681 has 4 divisors (see below), whose sum is σ = 2047837764. Its totient is φ = 1950321600.

The previous prime is 1999079611. The next prime is 1999079683. The reversal of 1999079681 is 1869709991.

1999079681 = 31615² + 31616².

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 999571456 + 999508225 = 31616^2 + 31615^2 .

It is a cyclic number.

It is not a de Polignac number, because 1999079681 - 2¹⁰ = 1999078657 is a prime.

It is a super-2 number, since 2×1999079681² = 7992639141974123522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1999079681.

It is not an unprimeable number, because it can be changed into a prime (1999079683) 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, 24378980 + ... + 24379061.

It is an arithmetic number, because the mean of its divisors is an integer number (511959441).

Almost surely, 2^1999079681 is an apocalyptic number.

1999079681 is the 31616-th centered square number.

It is an amenable number.

1999079681 is a deficient number, since it is larger than the sum of its proper divisors (48758083).

1999079681 is an equidigital number, since it uses as much as digits as its factorization.

1999079681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48758082.

The product of its (nonzero) digits is 2204496, while the sum is 59.

The square root of 1999079681 is about 44711.0688867980. The cubic root of 1999079681 is about 1259.7277653645.

The spelling of 1999079681 in words is "one billion, nine hundred ninety-nine million, seventy-nine thousand, six hundred eighty-one".