66661320161 has 2 divisors, whose sum is σ = 66661320162. Its totient is φ = 66661320160.

The previous prime is 66661320151. The next prime is 66661320169. The reversal of 66661320161 is 16102316666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60052443136 + 6608877025 = 245056^2 + 81295^2 .

It is a cyclic number.

It is not a de Polignac number, because 66661320161 - 2²⁶ = 66594211297 is a prime.

It is not a weakly prime, because it can be changed into another prime (66661320169) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33330660080 + 33330660081.

It is an arithmetic number, because the mean of its divisors is an integer number (33330660081).

Almost surely, 2^66661320161 is an apocalyptic number.

It is an amenable number.

66661320161 is a deficient number, since it is larger than the sum of its proper divisors (1).

66661320161 is an equidigital number, since it uses as much as digits as its factorization.

66661320161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 46656, while the sum is 38.

The spelling of 66661320161 in words is "sixty-six billion, six hundred sixty-one million, three hundred twenty thousand, one hundred sixty-one".