668552561 has 2 divisors, whose sum is σ = 668552562. Its totient is φ = 668552560.

The previous prime is 668552539. The next prime is 668552567. The reversal of 668552561 is 165255866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 624250225 + 44302336 = 24985^2 + 6656^2 .

It is a cyclic number.

It is not a de Polignac number, because 668552561 - 2¹⁴ = 668536177 is a prime.

It is not a weakly prime, because it can be changed into another prime (668552567) 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, 334276280 + 334276281.

It is an arithmetic number, because the mean of its divisors is an integer number (334276281).

Almost surely, 2^668552561 is an apocalyptic number.

It is an amenable number.

668552561 is a deficient number, since it is larger than the sum of its proper divisors (1).

668552561 is an equidigital number, since it uses as much as digits as its factorization.

668552561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432000, while the sum is 44.

The square root of 668552561 is about 25856.3833704561. The cubic root of 668552561 is about 874.4034294353.

The spelling of 668552561 in words is "six hundred sixty-eight million, five hundred fifty-two thousand, five hundred sixty-one".