166406561 has 4 divisors (see below), whose sum is σ = 166464324. Its totient is φ = 166348800.

The previous prime is 166406533. The next prime is 166406563. The reversal of 166406561 is 165604661.

166406561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165604661 = 73 ⋅2268557.

It can be written as a sum of positive squares in 2 ways, for example, as 146870161 + 19536400 = 12119^2 + 4420^2 .

It is a cyclic number.

It is not a de Polignac number, because 166406561 - 2⁶ = 166406497 is a prime.

It is a super-2 number, since 2×166406561² = 55382287087693442, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (166406563) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24320 + ... + 30401.

It is an arithmetic number, because the mean of its divisors is an integer number (41616081).

It is a Poulet number, since it divides 2^166406560-1.

Almost surely, 2^166406561 is an apocalyptic number.

It is an amenable number.

166406561 is a deficient number, since it is larger than the sum of its proper divisors (57763).

166406561 is an equidigital number, since it uses as much as digits as its factorization.

166406561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57762.

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 166406561 is about 12899.8667047377. The cubic root of 166406561 is about 550.0347757626.

The spelling of 166406561 in words is "one hundred sixty-six million, four hundred six thousand, five hundred sixty-one".