665643 has 16 divisors (see below), whose sum is σ = 1011456. Its totient is φ = 385440.

The previous prime is 665633. The next prime is 665659. The reversal of 665643 is 346566.

It is not a de Polignac number, because 665643 - 2⁸ = 665387 is a prime.

665643 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 665643.

It is not an unprimeable number, because it can be changed into a prime (665603) 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, 321 + ... + 1197.

It is an arithmetic number, because the mean of its divisors is an integer number (63216).

2⁶⁶⁵⁶⁴³ is an apocalyptic number.

665643 is a deficient number, since it is larger than the sum of its proper divisors (345813).

665643 is a wasteful number, since it uses less digits than its factorization.

665643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 914.

The product of its digits is 12960, while the sum is 30.

The square root of 665643 is about 815.8694748549. The cubic root of 665643 is about 87.3133108085.

The spelling of 665643 in words is "six hundred sixty-five thousand, six hundred forty-three".