1666722779 has 2 divisors, whose sum is σ = 1666722780. Its totient is φ = 1666722778.

The previous prime is 1666722763. The next prime is 1666722817. The reversal of 1666722779 is 9772276661.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1666722779 - 2⁴ = 1666722763 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1666722779.

It is not a weakly prime, because it can be changed into another prime (1666722179) 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, 833361389 + 833361390.

It is an arithmetic number, because the mean of its divisors is an integer number (833361390).

Almost surely, 2^1666722779 is an apocalyptic number.

1666722779 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666722779 is an equidigital number, since it uses as much as digits as its factorization.

1666722779 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2667168, while the sum is 53.

The square root of 1666722779 is about 40825.5162735268. The cubic root of 1666722779 is about 1185.6444070529.

The spelling of 1666722779 in words is "one billion, six hundred sixty-six million, seven hundred twenty-two thousand, seven hundred seventy-nine".