665864 has 8 divisors (see below), whose sum is σ = 1248510. Its totient is φ = 332928.

The previous prime is 665857. The next prime is 665897. The reversal of 665864 is 468566.

It can be written as a sum of positive squares in only one way, i.e., 372100 + 293764 = 610^2 + 542^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41609 + ... + 41624.

2⁶⁶⁵⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

665864 is a deficient number, since it is larger than the sum of its proper divisors (582646).

665864 is a wasteful number, since it uses less digits than its factorization.

665864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83239 (or 83235 counting only the distinct ones).

The product of its digits is 34560, while the sum is 35.

The square root of 665864 is about 816.0049019461. The cubic root of 665864 is about 87.3229726976.

The spelling of 665864 in words is "six hundred sixty-five thousand, eight hundred sixty-four".