666215257 has 2 divisors, whose sum is σ = 666215258. Its totient is φ = 666215256.

The previous prime is 666215219. The next prime is 666215279. The reversal of 666215257 is 752512666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 648415296 + 17799961 = 25464^2 + 4219^2 .

It is a cyclic number.

It is not a de Polignac number, because 666215257 - 2²³ = 657826649 is a prime.

It is not a weakly prime, because it can be changed into another prime (666215857) 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, 333107628 + 333107629.

It is an arithmetic number, because the mean of its divisors is an integer number (333107629).

Almost surely, 2^666215257 is an apocalyptic number.

It is an amenable number.

666215257 is a deficient number, since it is larger than the sum of its proper divisors (1).

666215257 is an equidigital number, since it uses as much as digits as its factorization.

666215257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 151200, while the sum is 40.

The square root of 666215257 is about 25811.1459838574. The cubic root of 666215257 is about 873.3832488838.

The spelling of 666215257 in words is "six hundred sixty-six million, two hundred fifteen thousand, two hundred fifty-seven".