166055666561 has 2 divisors, whose sum is σ = 166055666562. Its totient is φ = 166055666560.

The previous prime is 166055666531. The next prime is 166055666573. The reversal of 166055666561 is 165666550661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 164973256561 + 1082410000 = 406169^2 + 32900^2 .

It is a cyclic number.

It is not a de Polignac number, because 166055666561 - 2¹⁰ = 166055665537 is a prime.

It is not a weakly prime, because it can be changed into another prime (166055666531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83027833280 + 83027833281.

It is an arithmetic number, because the mean of its divisors is an integer number (83027833281).

Almost surely, 2^166055666561 is an apocalyptic number.

It is an amenable number.

166055666561 is a deficient number, since it is larger than the sum of its proper divisors (1).

166055666561 is an equidigital number, since it uses as much as digits as its factorization.

166055666561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832000, while the sum is 53.

The spelling of 166055666561 in words is "one hundred sixty-six billion, fifty-five million, six hundred sixty-six thousand, five hundred sixty-one".