666778979 has 2 divisors, whose sum is σ = 666778980. Its totient is φ = 666778978.

The previous prime is 666778939. The next prime is 666779021. The reversal of 666778979 is 979877666.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666778979 - 2²⁴ = 650001763 is a prime.

It is not a weakly prime, because it can be changed into another prime (666778939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333389489 + 333389490.

It is an arithmetic number, because the mean of its divisors is an integer number (333389490).

Almost surely, 2^666778979 is an apocalyptic number.

666778979 is a deficient number, since it is larger than the sum of its proper divisors (1).

666778979 is an equidigital number, since it uses as much as digits as its factorization.

666778979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48009024, while the sum is 65.

The square root of 666778979 is about 25822.0638021054. The cubic root of 666778979 is about 873.6295189119.

The spelling of 666778979 in words is "six hundred sixty-six million, seven hundred seventy-eight thousand, nine hundred seventy-nine".