666161 has 4 divisors (see below), whose sum is σ = 669300. Its totient is φ = 663024.

The previous prime is 666143. The next prime is 666167. The reversal of 666161 is 161666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 161666 = 2 ⋅80833.

It can be written as a sum of positive squares in 2 ways, for example, as 600625 + 65536 = 775^2 + 256^2 .

It is a cyclic number.

It is not a de Polignac number, because 666161 - 2¹⁴ = 649777 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 666161.

It is not an unprimeable number, because it can be changed into a prime (666167) 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, 1226 + ... + 1683.

It is an arithmetic number, because the mean of its divisors is an integer number (167325).

2⁶⁶⁶¹⁶¹ is an apocalyptic number.

It is an amenable number.

666161 is a deficient number, since it is larger than the sum of its proper divisors (3139).

666161 is a wasteful number, since it uses less digits than its factorization.

666161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3138.

The product of its digits is 1296, while the sum is 26.

The square root of 666161 is about 816.1868658585. The cubic root of 666161 is about 87.3359538609.

The spelling of 666161 in words is "six hundred sixty-six thousand, one hundred sixty-one".