66777777791 has 2 divisors, whose sum is σ = 66777777792. Its totient is φ = 66777777790.

The previous prime is 66777777779. The next prime is 66777777793. The reversal of 66777777791 is 19777777766.

66777777791 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66777777791 - 2³⁰ = 65704035967 is a prime.

Together with 66777777793, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66777777793) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33388888895 + 33388888896.

It is an arithmetic number, because the mean of its divisors is an integer number (33388888896).

Almost surely, 2^66777777791 is an apocalyptic number.

66777777791 is a deficient number, since it is larger than the sum of its proper divisors (1).

66777777791 is an equidigital number, since it uses as much as digits as its factorization.

66777777791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 266827932, while the sum is 71.

The spelling of 66777777791 in words is "sixty-six billion, seven hundred seventy-seven million, seven hundred seventy-seven thousand, seven hundred ninety-one".