9966321665 has 16 divisors (see below), whose sum is σ = 12514581648. Its totient is φ = 7611192576.

The previous prime is 9966321647. The next prime is 9966321671. The reversal of 9966321665 is 5661236699.

It can be written as a sum of positive squares in 8 ways, for example, as 2472476176 + 7493845489 = 49724^2 + 86567^2 .

It is a cyclic number.

It is not a de Polignac number, because 9966321665 - 2¹⁴ = 9966305281 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (53).

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 498422 + ... + 518031.

It is an arithmetic number, because the mean of its divisors is an integer number (782161353).

It is a Proth number, since it is equal to 76037 ⋅ 2¹⁷ + 1 and 76037 < 2¹⁷.

Almost surely, 2^9966321665 is an apocalyptic number.

It is an amenable number.

9966321665 is a deficient number, since it is larger than the sum of its proper divisors (2548259983).

9966321665 is a wasteful number, since it uses less digits than its factorization.

9966321665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1016548.

The product of its digits is 3149280, while the sum is 53.

The square root of 9966321665 is about 99831.4663069716. The cubic root of 9966321665 is about 2152.0133773606.

The spelling of 9966321665 in words is "nine billion, nine hundred sixty-six million, three hundred twenty-one thousand, six hundred sixty-five".