66443540161 has 2 divisors, whose sum is σ = 66443540162. Its totient is φ = 66443540160.

The previous prime is 66443540131. The next prime is 66443540237. The reversal of 66443540161 is 16104534466.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65244995761 + 1198544400 = 255431^2 + 34620^2 .

It is a cyclic number.

It is not a de Polignac number, because 66443540161 - 2⁹ = 66443539649 is a prime.

It is not a weakly prime, because it can be changed into another prime (66443540131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33221770080 + 33221770081.

It is an arithmetic number, because the mean of its divisors is an integer number (33221770081).

Almost surely, 2^66443540161 is an apocalyptic number.

It is an amenable number.

66443540161 is a deficient number, since it is larger than the sum of its proper divisors (1).

66443540161 is an equidigital number, since it uses as much as digits as its factorization.

66443540161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 207360, while the sum is 40.

The spelling of 66443540161 in words is "sixty-six billion, four hundred forty-three million, five hundred forty thousand, one hundred sixty-one".