66755055781 has 2 divisors, whose sum is σ = 66755055782. Its totient is φ = 66755055780.

The previous prime is 66755055761. The next prime is 66755055799. The reversal of 66755055781 is 18755055766.

66755055781 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 can be written as a sum of positive squares in only one way, i.e., 37532862756 + 29222193025 = 193734^2 + 170945^2 .

It is a cyclic number.

It is not a de Polignac number, because 66755055781 - 2¹³ = 66755047589 is a prime.

It is a super-2 number, since 2×66755055781² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66755055761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33377527890 + 33377527891.

It is an arithmetic number, because the mean of its divisors is an integer number (33377527891).

Almost surely, 2^66755055781 is an apocalyptic number.

It is an amenable number.

66755055781 is a deficient number, since it is larger than the sum of its proper divisors (1).

66755055781 is an equidigital number, since it uses as much as digits as its factorization.

66755055781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8820000, while the sum is 55.

The spelling of 66755055781 in words is "sixty-six billion, seven hundred fifty-five million, fifty-five thousand, seven hundred eighty-one".