66778210721977 has 2 divisors, whose sum is σ = 66778210721978. Its totient is φ = 66778210721976.

The previous prime is 66778210721969. The next prime is 66778210722031. The reversal of 66778210721977 is 77912701287766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 44402245577001 + 22375965144976 = 6663501^2 + 4730324^2 .

It is a cyclic number.

It is not a de Polignac number, because 66778210721977 - 2³ = 66778210721969 is a prime.

It is not a weakly prime, because it can be changed into another prime (66778210721177) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33389105360988 + 33389105360989.

It is an arithmetic number, because the mean of its divisors is an integer number (33389105360989).

Almost surely, 2^{66778210721977} is an apocalyptic number.

It is an amenable number.

66778210721977 is a deficient number, since it is larger than the sum of its proper divisors (1).

66778210721977 is an equidigital number, since it uses as much as digits as its factorization.

66778210721977 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 174254976, while the sum is 70.

The spelling of 66778210721977 in words is "sixty-six trillion, seven hundred seventy-eight billion, two hundred ten million, seven hundred twenty-one thousand, nine hundred seventy-seven".