665644 has 12 divisors (see below), whose sum is σ = 1331344. Its totient is φ = 285264.

The previous prime is 665633. The next prime is 665659. The reversal of 665644 is 446566.

665644 is an admirable number.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

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 3 ways as a sum of consecutive naturals, for example, 11859 + ... + 11914.

2⁶⁶⁵⁶⁴⁴ is an apocalyptic number.

It is an amenable number.

665644 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

665644 is a wasteful number, since it uses less digits than its factorization.

665644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23784 (or 23782 counting only the distinct ones).

The product of its digits is 17280, while the sum is 31.

The square root of 665644 is about 815.8700876978. The cubic root of 665644 is about 87.3133545323.

It can be divided in two parts, 66564 and 4, that multiplied together give a square (266256 = 516²).

The spelling of 665644 in words is "six hundred sixty-five thousand, six hundred forty-four".