1666220722009 has 2 divisors, whose sum is σ = 1666220722010. Its totient is φ = 1666220722008.

The previous prime is 1666220722007. The next prime is 1666220722051. The reversal of 1666220722009 is 9002270226661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1470224150784 + 195996571225 = 1212528^2 + 442715^2 .

It is an emirp because it is prime and its reverse (9002270226661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1666220722009 - 2¹ = 1666220722007 is a prime.

Together with 1666220722007, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1666220722007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833110361004 + 833110361005.

It is an arithmetic number, because the mean of its divisors is an integer number (833110361005).

Almost surely, 2^{1666220722009} is an apocalyptic number.

It is an amenable number.

1666220722009 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666220722009 is an equidigital number, since it uses as much as digits as its factorization.

1666220722009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 217728, while the sum is 43.

The spelling of 1666220722009 in words is "one trillion, six hundred sixty-six billion, two hundred twenty million, seven hundred twenty-two thousand, nine".