2165661 has 12 divisors (see below), whose sum is σ = 3205020. Its totient is φ = 1408320.

The previous prime is 2165659. The next prime is 2165663. The reversal of 2165661 is 1665612.

It is a happy number.

2165661 is a `hidden beast` number, since 2 + 1 + 656 + 6 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (2165659) and next prime (2165663).

It can be written as a sum of positive squares in 2 ways, for example, as 152100 + 2013561 = 390^2 + 1419^2 .

It is not a de Polignac number, because 2165661 - 2¹ = 2165659 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2165663) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2566 + ... + 3303.

It is an arithmetic number, because the mean of its divisors is an integer number (267085).

2^2165661 is an apocalyptic number.

It is an amenable number.

2165661 is a deficient number, since it is larger than the sum of its proper divisors (1039359).

2165661 is a wasteful number, since it uses less digits than its factorization.

2165661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5916 (or 5913 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 2165661 is about 1471.6184967579. The cubic root of 2165661 is about 129.3789111749.

The spelling of 2165661 in words is "two million, one hundred sixty-five thousand, six hundred sixty-one".