665718779 has 16 divisors (see below), whose sum is σ = 734093280. Its totient is φ = 598690560.

The previous prime is 665718749. The next prime is 665718829. The reversal of 665718779 is 977817566.

It is a cyclic number.

It is not a de Polignac number, because 665718779 - 2¹⁶ = 665653243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665718709) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 463847 + ... + 465279.

It is an arithmetic number, because the mean of its divisors is an integer number (45880830).

Almost surely, 2^665718779 is an apocalyptic number.

665718779 is a deficient number, since it is larger than the sum of its proper divisors (68374501).

665718779 is a wasteful number, since it uses less digits than its factorization.

665718779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1870.

The product of its digits is 4445280, while the sum is 56.

The square root of 665718779 is about 25801.5266796366. The cubic root of 665718779 is about 873.1662402809.

The spelling of 665718779 in words is "six hundred sixty-five million, seven hundred eighteen thousand, seven hundred seventy-nine".