2001665 has 8 divisors (see below), whose sum is σ = 2543400. Its totient is φ = 1507072.

The previous prime is 2001653. The next prime is 2001673. The reversal of 2001665 is 5661002.

2001665 = T₃₂₆ + T₃₂₇ + ... + T₃₅₉.

It can be written as a sum of positive squares in 4 ways, for example, as 16384 + 1985281 = 128^2 + 1409^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2001665 - 2⁸ = 2001409 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11690 + ... + 11859.

It is an arithmetic number, because the mean of its divisors is an integer number (317925).

2^2001665 is an apocalyptic number.

It is an amenable number.

2001665 is a deficient number, since it is larger than the sum of its proper divisors (541735).

2001665 is a wasteful number, since it uses less digits than its factorization.

2001665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23571.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 2001665 is about 1414.8021063032. The cubic root of 2001665 is about 126.0270581009.

Adding to 2001665 its reverse (5661002), we get a palindrome (7662667).

The spelling of 2001665 in words is "two million, one thousand, six hundred sixty-five".