166255561 has 4 divisors (see below), whose sum is σ = 168981124. Its totient is φ = 163530000.

The previous prime is 166255553. The next prime is 166255577. The reversal of 166255561 is 165552661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165552661 = 3347 ⋅49463.

It can be written as a sum of positive squares in 2 ways, for example, as 55353600 + 110901961 = 7440^2 + 10531^2 .

It is a cyclic number.

It is not a de Polignac number, because 166255561 - 2³ = 166255553 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 166255561.

It is not an unprimeable number, because it can be changed into a prime (166255361) 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, 1362690 + ... + 1362811.

It is an arithmetic number, because the mean of its divisors is an integer number (42245281).

Almost surely, 2^166255561 is an apocalyptic number.

It is an amenable number.

166255561 is a deficient number, since it is larger than the sum of its proper divisors (2725563).

166255561 is an equidigital number, since it uses as much as digits as its factorization.

166255561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2725562.

The product of its digits is 54000, while the sum is 37.

The square root of 166255561 is about 12894.0126027548. The cubic root of 166255561 is about 549.8683552697.

The spelling of 166255561 in words is "one hundred sixty-six million, two hundred fifty-five thousand, five hundred sixty-one".