66681020257 has 2 divisors, whose sum is σ = 66681020258. Its totient is φ = 66681020256.

The previous prime is 66681020249. The next prime is 66681020279. The reversal of 66681020257 is 75202018666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55112727121 + 11568293136 = 234761^2 + 107556^2 .

It is a cyclic number.

It is not a de Polignac number, because 66681020257 - 2³ = 66681020249 is a prime.

It is not a weakly prime, because it can be changed into another prime (66681020297) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33340510128 + 33340510129.

It is an arithmetic number, because the mean of its divisors is an integer number (33340510129).

Almost surely, 2^66681020257 is an apocalyptic number.

It is an amenable number.

66681020257 is a deficient number, since it is larger than the sum of its proper divisors (1).

66681020257 is an equidigital number, since it uses as much as digits as its factorization.

66681020257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 241920, while the sum is 43.

The spelling of 66681020257 in words is "sixty-six billion, six hundred eighty-one million, twenty thousand, two hundred fifty-seven".