666505657 has 2 divisors, whose sum is σ = 666505658. Its totient is φ = 666505656.

The previous prime is 666505639. The next prime is 666505667. The reversal of 666505657 is 756505666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 664556841 + 1948816 = 25779^2 + 1396^2 .

It is a cyclic number.

It is not a de Polignac number, because 666505657 - 2⁷ = 666505529 is a prime.

It is not a weakly prime, because it can be changed into another prime (666505607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333252828 + 333252829.

It is an arithmetic number, because the mean of its divisors is an integer number (333252829).

Almost surely, 2^666505657 is an apocalyptic number.

It is an amenable number.

666505657 is a deficient number, since it is larger than the sum of its proper divisors (1).

666505657 is an equidigital number, since it uses as much as digits as its factorization.

666505657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1134000, while the sum is 46.

The square root of 666505657 is about 25816.7708476486. The cubic root of 666505657 is about 873.5101316241.

Subtracting 666505657 from its reverse (756505666), we obtain a palindrome (90000009).

The spelling of 666505657 in words is "six hundred sixty-six million, five hundred five thousand, six hundred fifty-seven".