666657217 has 2 divisors, whose sum is σ = 666657218. Its totient is φ = 666657216.

The previous prime is 666657203. The next prime is 666657223. The reversal of 666657217 is 712756666.

666657217 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 452795841 + 213861376 = 21279^2 + 14624^2 .

It is a cyclic number.

It is not a de Polignac number, because 666657217 - 2¹¹ = 666655169 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (666657317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333328608 + 333328609.

It is an arithmetic number, because the mean of its divisors is an integer number (333328609).

Almost surely, 2^666657217 is an apocalyptic number.

It is an amenable number.

666657217 is a deficient number, since it is larger than the sum of its proper divisors (1).

666657217 is an equidigital number, since it uses as much as digits as its factorization.

666657217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 635040, while the sum is 46.

The square root of 666657217 is about 25819.7059820595. The cubic root of 666657217 is about 873.5763371947.

The spelling of 666657217 in words is "six hundred sixty-six million, six hundred fifty-seven thousand, two hundred seventeen".