666733409 has 2 divisors, whose sum is σ = 666733410. Its totient is φ = 666733408.

The previous prime is 666733393. The next prime is 666733411. The reversal of 666733409 is 904337666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 666672400 + 61009 = 25820^2 + 247^2 .

It is a cyclic number.

It is not a de Polignac number, because 666733409 - 2⁴ = 666733393 is a prime.

It is a super-2 number, since 2×666733409² = 889066877353522562, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 666733411, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 666733409.

It is not a weakly prime, because it can be changed into another prime (666733609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333366704 + 333366705.

It is an arithmetic number, because the mean of its divisors is an integer number (333366705).

Almost surely, 2^666733409 is an apocalyptic number.

It is an amenable number.

666733409 is a deficient number, since it is larger than the sum of its proper divisors (1).

666733409 is an equidigital number, since it uses as much as digits as its factorization.

666733409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 489888, while the sum is 44.

The square root of 666733409 is about 25821.1814020970. The cubic root of 666733409 is about 873.6096161628.

The spelling of 666733409 in words is "six hundred sixty-six million, seven hundred thirty-three thousand, four hundred nine".