665055611021 has 2 divisors, whose sum is σ = 665055611022. Its totient is φ = 665055611020.

The previous prime is 665055611009. The next prime is 665055611029. The reversal of 665055611021 is 120116550566.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 510303066025 + 154752544996 = 714355^2 + 393386^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665055611021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665055611029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332527805510 + 332527805511.

It is an arithmetic number, because the mean of its divisors is an integer number (332527805511).

Almost surely, 2^665055611021 is an apocalyptic number.

It is an amenable number.

665055611021 is a deficient number, since it is larger than the sum of its proper divisors (1).

665055611021 is an equidigital number, since it uses as much as digits as its factorization.

665055611021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 54000, while the sum is 38.

The spelling of 665055611021 in words is "six hundred sixty-five billion, fifty-five million, six hundred eleven thousand, twenty-one".