668216779 has 2 divisors, whose sum is σ = 668216780. Its totient is φ = 668216778.

The previous prime is 668216767. The next prime is 668216789. The reversal of 668216779 is 977612866.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 668216779 - 2⁷ = 668216651 is a prime.

It is not a weakly prime, because it can be changed into another prime (668216789) 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, 334108389 + 334108390.

It is an arithmetic number, because the mean of its divisors is an integer number (334108390).

Almost surely, 2^668216779 is an apocalyptic number.

668216779 is a deficient number, since it is larger than the sum of its proper divisors (1).

668216779 is an equidigital number, since it uses as much as digits as its factorization.

668216779 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1524096, while the sum is 52.

The square root of 668216779 is about 25849.8893421229. The cubic root of 668216779 is about 874.2570145691.

The spelling of 668216779 in words is "six hundred sixty-eight million, two hundred sixteen thousand, seven hundred seventy-nine".