166721081 has 2 divisors, whose sum is σ = 166721082. Its totient is φ = 166721080.

The previous prime is 166721077. The next prime is 166721099. The reversal of 166721081 is 180127661.

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., 98823481 + 67897600 = 9941^2 + 8240^2 .

It is a cyclic number.

It is not a de Polignac number, because 166721081 - 2² = 166721077 is a prime.

It is a super-2 number, since 2×166721081² = 55591837699617122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (166721011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83360540 + 83360541.

It is an arithmetic number, because the mean of its divisors is an integer number (83360541).

Almost surely, 2^166721081 is an apocalyptic number.

It is an amenable number.

166721081 is a deficient number, since it is larger than the sum of its proper divisors (1).

166721081 is an equidigital number, since it uses as much as digits as its factorization.

166721081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 166721081 is about 12912.0517734402. The cubic root of 166721081 is about 550.3810923558.

The spelling of 166721081 in words is "one hundred sixty-six million, seven hundred twenty-one thousand, eighty-one".