1999866665 has 4 divisors (see below), whose sum is σ = 2399840004. Its totient is φ = 1599893328.

The previous prime is 1999866611. The next prime is 1999866667. The reversal of 1999866665 is 5666689991.

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 236790544 + 1763076121 = 15388^2 + 41989^2 .

It is a cyclic number.

It is not a de Polignac number, because 1999866665 - 2⁶ = 1999866601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1999866667) 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 3 ways as a sum of consecutive naturals, for example, 199986662 + ... + 199986671.

It is an arithmetic number, because the mean of its divisors is an integer number (599960001).

Almost surely, 2^1999866665 is an apocalyptic number.

It is an amenable number.

1999866665 is a deficient number, since it is larger than the sum of its proper divisors (399973339).

1999866665 is an equidigital number, since it uses as much as digits as its factorization.

1999866665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 399973338.

The product of its digits is 37791360, while the sum is 65.

The square root of 1999866665 is about 44719.8687945302. The cubic root of 1999866665 is about 1259.8930506771.

The spelling of 1999866665 in words is "one billion, nine hundred ninety-nine million, eight hundred sixty-six thousand, six hundred sixty-five".