665638 has 8 divisors (see below), whose sum is σ = 1015560. Its totient is φ = 327120.

The previous prime is 665633. The next prime is 665659. The reversal of 665638 is 836566.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665633) by changing a digit.

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, 2703 + ... + 2938.

It is an arithmetic number, because the mean of its divisors is an integer number (126945).

2⁶⁶⁵⁶³⁸ is an apocalyptic number.

665638 is a deficient number, since it is larger than the sum of its proper divisors (349922).

665638 is a wasteful number, since it uses less digits than its factorization.

665638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5702.

The product of its digits is 25920, while the sum is 34.

The square root of 665638 is about 815.8664106335. The cubic root of 665638 is about 87.3130921890.

It can be divided in two parts, 6 and 65638, that multiplied together give a triangular number (393828 = T₈₈₇).

The spelling of 665638 in words is "six hundred sixty-five thousand, six hundred thirty-eight".