766666661 has 4 divisors (see below), whose sum is σ = 767592300. Its totient is φ = 765741024.

The previous prime is 766666633. The next prime is 766666669. The reversal of 766666661 is 166666667.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 545222500 + 221444161 = 23350^2 + 14881^2 .

It is a cyclic number.

It is not a de Polignac number, because 766666661 - 2⁶ = 766666597 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (766666669) 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 in 3 ways as a sum of consecutive naturals, for example, 461576 + ... + 463233.

It is an arithmetic number, because the mean of its divisors is an integer number (191898075).

Almost surely, 2^766666661 is an apocalyptic number.

It is an amenable number.

766666661 is a deficient number, since it is larger than the sum of its proper divisors (925639).

766666661 is an equidigital number, since it uses as much as digits as its factorization.

766666661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 925638.

The product of its digits is 1959552, while the sum is 50.

The square root of 766666661 is about 27688.7461073989. The cubic root of 766666661 is about 915.2411245041.

It can be divided in two parts, 76666666 and 1, that added together give a palindrome (76666667).

The spelling of 766666661 in words is "seven hundred sixty-six million, six hundred sixty-six thousand, six hundred sixty-one".