166315781 has 2 divisors, whose sum is σ = 166315782. Its totient is φ = 166315780.

The previous prime is 166315763. The next prime is 166315817. The reversal of 166315781 is 187513661.

166315781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

Together with next prime (166315817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 134212225 + 32103556 = 11585^2 + 5666^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-166315781 is a prime.

It is a super-2 number, since 2×166315781² = 55321878019279922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166315711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83157890 + 83157891.

It is an arithmetic number, because the mean of its divisors is an integer number (83157891).

Almost surely, 2^166315781 is an apocalyptic number.

It is an amenable number.

166315781 is a deficient number, since it is larger than the sum of its proper divisors (1).

166315781 is an equidigital number, since it uses as much as digits as its factorization.

166315781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 38.

The square root of 166315781 is about 12896.3475837153. The cubic root of 166315781 is about 549.9347371598.

The spelling of 166315781 in words is "one hundred sixty-six million, three hundred fifteen thousand, seven hundred eighty-one".