666609999 has 16 divisors (see below), whose sum is σ = 979219584. Its totient is φ = 400004000.

The previous prime is 666609997. The next prime is 666610027. The reversal of 666609999 is 999906666.

It is not a de Polignac number, because 666609999 - 2¹ = 666609997 is a prime.

666609999 is a strobogrammatic number because it is the same when read upside-down.

666609999 is a modest number, since divided by 9999 gives 6666 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666609997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 96669 + ... + 103334.

It is an arithmetic number, because the mean of its divisors is an integer number (61201224).

Almost surely, 2^666609999 is an apocalyptic number.

666609999 is a deficient number, since it is larger than the sum of its proper divisors (312609585).

666609999 is a wasteful number, since it uses less digits than its factorization.

666609999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200118.

The product of its (nonzero) digits is 8503056, while the sum is 60.

The square root of 666609999 is about 25818.7915867494. The cubic root of 666609999 is about 873.5557121517. Note that the first 3 decimals are identical.

The spelling of 666609999 in words is "six hundred sixty-six million, six hundred nine thousand, nine hundred ninety-nine".