1999806566 has 4 divisors (see below), whose sum is σ = 2999709852. Its totient is φ = 999903282.

The previous prime is 1999806551. The next prime is 1999806581. The reversal of 1999806566 is 6656089991.

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

It is an interprime number because it is at equal distance from previous prime (1999806551) and next prime (1999806581).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499951640 + ... + 499951643.

It is an arithmetic number, because the mean of its divisors is an integer number (749927463).

Almost surely, 2^1999806566 is an apocalyptic number.

1999806566 is a deficient number, since it is larger than the sum of its proper divisors (999903286).

1999806566 is an equidigital number, since it uses as much as digits as its factorization.

1999806566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 999903285.

The product of its (nonzero) digits is 6298560, while the sum is 59.

The square root of 1999806566 is about 44719.1968398360. The cubic root of 1999806566 is about 1259.8804299906.

The spelling of 1999806566 in words is "one billion, nine hundred ninety-nine million, eight hundred six thousand, five hundred sixty-six".