999999999999666 has 48 divisors (see below), whose sum is σ = 2236520785036824. Its totient is φ = 322678007914752.

The previous prime is 999999999999659. The next prime is 999999999999809. The reversal of 999999999999666 is 666999999999999.

It can be written as a sum of positive squares in 4 ways, for example, as 790407060844041 + 209592939155625 = 28114179^2 + 14477325^2 .

It is a super-9 number, since 9×999999999999666⁹ (a number of 136 digits) contains 999999999 as substring. Note that it is a super-d number also for d = 2.

It is a nude number because it is divisible by every one of its digits.

It is a Curzon number.

It is a nialpdrome in base 10.

It is a zygodrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 999999999999666.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3810786315 + ... + 3811048718.

Almost surely, 2^{999999999999666} is an apocalyptic number.

999999999999666 is an abundant number, since it is smaller than the sum of its proper divisors (1236520785037158).

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

999999999999666 is a wasteful number, since it uses less digits than its factorization.

999999999999666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7621835275 (or 7621835272 counting only the distinct ones).

The product of its digits is 61004779879896, while the sum is 126.

The spelling of 999999999999666 in words is "nine hundred ninety-nine trillion, nine hundred ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, six hundred sixty-six".