665778091 has 4 divisors (see below), whose sum is σ = 726303384. Its totient is φ = 605252800.

The previous prime is 665778053. The next prime is 665778133. The reversal of 665778091 is 190877566.

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 665778091 - 2¹¹ = 665776043 is a prime.

It is a Duffinian number.

It is a zygodrome in base 7.

It is not an unprimeable number, because it can be changed into a prime (665776091) 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, 30262630 + ... + 30262651.

It is an arithmetic number, because the mean of its divisors is an integer number (181575846).

Almost surely, 2^665778091 is an apocalyptic number.

665778091 is a deficient number, since it is larger than the sum of its proper divisors (60525293).

665778091 is a wasteful number, since it uses less digits than its factorization.

665778091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60525292.

The product of its (nonzero) digits is 635040, while the sum is 49.

The square root of 665778091 is about 25802.6760433874. The cubic root of 665778091 is about 873.1921709991.

It can be divided in two parts, 6657 and 78091, that added together give a palindrome (84748).

The spelling of 665778091 in words is "six hundred sixty-five million, seven hundred seventy-eight thousand, ninety-one".