9999999666 has 24 divisors (see below), whose sum is σ = 22469136144.
Its totient is φ = 3333333060.
The previous prime is 9999999661. The next prime is 9999999673. The reversal of 9999999666 is 6669999999.
It is a super-2 number, since 2×99999996662 (a number of 21 digits) contains 22 as substring.
It is a Harshad number since it is a multiple of its sum of digits (81).
It is a nude number because it is divisible by every one of its digits.
It is a nialpdrome in base 10.
It is a zygodrome in base 10.
It is not an unprimeable number, because it can be changed into a prime (9999999661) by changing a digit.
It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10287580 + ... + 10288551.
It is an arithmetic number, because the mean of its divisors is an integer number (936214006).
Almost surely, 29999999666 is an apocalyptic number.
9999999666 is an abundant number, since it is smaller than the sum of its proper divisors (12469136478).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
9999999666 is a wasteful number, since it uses less digits than its factorization.
9999999666 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 20576148 (or 20576136 counting only the distinct ones).
The product of its digits is 1033121304, while the sum is 81.
The square root of 9999999666 is about 99999.9983300000.
The cubic root of 9999999666 is about 2154.4346660458.
The spelling of 9999999666 in words is "nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, six hundred sixty-six".