2181665 has 16 divisors (see below), whose sum is σ = 2785536. Its totient is φ = 1636800.

The previous prime is 2181659. The next prime is 2181671. The reversal of 2181665 is 5661812.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (2181659) and next prime (2181671).

It is not a de Polignac number, because 2181665 - 2⁴ = 2181649 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6860 + ... + 7170.

It is an arithmetic number, because the mean of its divisors is an integer number (174096).

2^2181665 is an apocalyptic number.

It is an amenable number.

2181665 is a deficient number, since it is larger than the sum of its proper divisors (603871).

2181665 is a wasteful number, since it uses less digits than its factorization.

2181665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400.

The product of its digits is 2880, while the sum is 29.

The square root of 2181665 is about 1477.0460385513. The cubic root of 2181665 is about 129.6968280415.

The spelling of 2181665 in words is "two million, one hundred eighty-one thousand, six hundred sixty-five".