1640665 has 16 divisors (see below), whose sum is σ = 2173248. Its totient is φ = 1181376.

The previous prime is 1640663. The next prime is 1640677. The reversal of 1640665 is 5660461.

It is a cyclic number.

It is not a de Polignac number, because 1640665 - 2¹ = 1640663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1640663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2502 + ... + 3088.

It is an arithmetic number, because the mean of its divisors is an integer number (135828).

2^1640665 is an apocalyptic number.

It is an amenable number.

1640665 is a deficient number, since it is larger than the sum of its proper divisors (532583).

1640665 is a wasteful number, since it uses less digits than its factorization.

1640665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 648.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 1640665 is about 1280.8844600509. The cubic root of 1640665 is about 117.9433080157.

It can be divided in two parts, 16406 and 65, that added together give a triangular number (16471 = T₁₈₁).

The spelling of 1640665 in words is "one million, six hundred forty thousand, six hundred sixty-five".