666665161 has 2 divisors, whose sum is σ = 666665162. Its totient is φ = 666665160.

The previous prime is 666665159. The next prime is 666665171. The reversal of 666665161 is 161566666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 651015225 + 15649936 = 25515^2 + 3956^2 .

It is a cyclic number.

It is not a de Polignac number, because 666665161 - 2¹ = 666665159 is a prime.

Together with 666665159, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (666665171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333332580 + 333332581.

It is an arithmetic number, because the mean of its divisors is an integer number (333332581).

Almost surely, 2^666665161 is an apocalyptic number.

It is an amenable number.

666665161 is a deficient number, since it is larger than the sum of its proper divisors (1).

666665161 is an equidigital number, since it uses as much as digits as its factorization.

666665161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 233280, while the sum is 43.

The square root of 666665161 is about 25819.8598175900. The cubic root of 666665161 is about 873.5798070753.

The spelling of 666665161 in words is "six hundred sixty-six million, six hundred sixty-five thousand, one hundred sixty-one".