666678779 has 4 divisors (see below), whose sum is σ = 717961776. Its totient is φ = 615395784.

The previous prime is 666678773. The next prime is 666678787. The reversal of 666678779 is 977876666.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 666678779 - 2⁴ = 666678763 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666678773) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25641479 + ... + 25641504.

It is an arithmetic number, because the mean of its divisors is an integer number (179490444).

Almost surely, 2^666678779 is an apocalyptic number.

666678779 is a deficient number, since it is larger than the sum of its proper divisors (51282997).

666678779 is a wasteful number, since it uses less digits than its factorization.

666678779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51282996.

The product of its digits is 32006016, while the sum is 62.

The square root of 666678779 is about 25820.1235279772. The cubic root of 666678779 is about 873.5857552531.

The spelling of 666678779 in words is "six hundred sixty-six million, six hundred seventy-eight thousand, seven hundred seventy-nine".