6666766621 has 2 divisors, whose sum is σ = 6666766622. Its totient is φ = 6666766620.

The previous prime is 6666766609. The next prime is 6666766643. The reversal of 6666766621 is 1266676666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3551564025 + 3115202596 = 59595^2 + 55814^2 .

It is a cyclic number.

It is not a de Polignac number, because 6666766621 - 2⁹ = 6666766109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6666766681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3333383310 + 3333383311.

It is an arithmetic number, because the mean of its divisors is an integer number (3333383311).

Almost surely, 2^6666766621 is an apocalyptic number.

It is an amenable number.

6666766621 is a deficient number, since it is larger than the sum of its proper divisors (1).

6666766621 is an equidigital number, since it uses as much as digits as its factorization.

6666766621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3919104, while the sum is 52.

The square root of 6666766621 is about 81650.2701832639. The cubic root of 6666766621 is about 1882.0814637779.

The spelling of 6666766621 in words is "six billion, six hundred sixty-six million, seven hundred sixty-six thousand, six hundred twenty-one".