166165561 has 4 divisors (see below), whose sum is σ = 168645712. Its totient is φ = 163685412.

The previous prime is 166165523. The next prime is 166165567. The reversal of 166165561 is 165561661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 166165561 - 2¹¹ = 166163513 is a prime.

It is a super-2 number, since 2×166165561² = 55221987324889442, which contains 22 as substring.

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 166165561.

It is not an unprimeable number, because it can be changed into a prime (166165567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1239975 + ... + 1240108.

It is an arithmetic number, because the mean of its divisors is an integer number (42161428).

Almost surely, 2^166165561 is an apocalyptic number.

It is an amenable number.

166165561 is a deficient number, since it is larger than the sum of its proper divisors (2480151).

166165561 is an equidigital number, since it uses as much as digits as its factorization.

166165561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2480150.

The product of its digits is 32400, while the sum is 37.

The square root of 166165561 is about 12890.5221383775. The cubic root of 166165561 is about 549.7691163144.

The spelling of 166165561 in words is "one hundred sixty-six million, one hundred sixty-five thousand, five hundred sixty-one".