666241909 has 2 divisors, whose sum is σ = 666241910. Its totient is φ = 666241908.

The previous prime is 666241907. The next prime is 666241949. The reversal of 666241909 is 909142666.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 348867684 + 317374225 = 18678^2 + 17815^2 .

It is a cyclic number.

It is not a de Polignac number, because 666241909 - 2¹ = 666241907 is a prime.

Together with 666241907, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666241907) 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, 333120954 + 333120955.

It is an arithmetic number, because the mean of its divisors is an integer number (333120955).

Almost surely, 2^666241909 is an apocalyptic number.

It is an amenable number.

666241909 is a deficient number, since it is larger than the sum of its proper divisors (1).

666241909 is an equidigital number, since it uses as much as digits as its factorization.

666241909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 139968, while the sum is 43.

The square root of 666241909 is about 25811.6622672776. The cubic root of 666241909 is about 873.3948953198.

The spelling of 666241909 in words is "six hundred sixty-six million, two hundred forty-one thousand, nine hundred nine".