666657281 has 2 divisors, whose sum is σ = 666657282. Its totient is φ = 666657280.

The previous prime is 666657239. The next prime is 666657293. The reversal of 666657281 is 182756666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 657409600 + 9247681 = 25640^2 + 3041^2 .

It is a cyclic number.

It is not a de Polignac number, because 666657281 - 2⁶ = 666657217 is a prime.

It is a super-2 number, since 2×666657281² = 888863860620625922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (666857281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333328640 + 333328641.

It is an arithmetic number, because the mean of its divisors is an integer number (333328641).

Almost surely, 2^666657281 is an apocalyptic number.

It is an amenable number.

666657281 is a deficient number, since it is larger than the sum of its proper divisors (1).

666657281 is an equidigital number, since it uses as much as digits as its factorization.

666657281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 725760, while the sum is 47.

The square root of 666657281 is about 25819.7072214229. The cubic root of 666657281 is about 873.5763651495.

The spelling of 666657281 in words is "six hundred sixty-six million, six hundred fifty-seven thousand, two hundred eighty-one".