166866812621 has 2 divisors, whose sum is σ = 166866812622. Its totient is φ = 166866812620.

The previous prime is 166866812573. The next prime is 166866812669. The reversal of 166866812621 is 126218668661.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (166866812573) and next prime (166866812669).

It can be written as a sum of positive squares in only one way, i.e., 98464164100 + 68402648521 = 313790^2 + 261539^2 .

It is a cyclic number.

It is not a de Polignac number, because 166866812621 - 2⁶ = 166866812557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166866812221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83433406310 + 83433406311.

It is an arithmetic number, because the mean of its divisors is an integer number (83433406311).

Almost surely, 2^166866812621 is an apocalyptic number.

It is an amenable number.

166866812621 is a deficient number, since it is larger than the sum of its proper divisors (1).

166866812621 is an equidigital number, since it uses as much as digits as its factorization.

166866812621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1990656, while the sum is 53.

The spelling of 166866812621 in words is "one hundred sixty-six billion, eight hundred sixty-six million, eight hundred twelve thousand, six hundred twenty-one".