665863 has 6 divisors (see below), whose sum is σ = 732032. Its totient is φ = 605220.

The previous prime is 665857. The next prime is 665897. The reversal of 665863 is 368566.

It is not a de Polignac number, because 665863 - 2⁹ = 665351 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665803) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2631 + ... + 2872.

2⁶⁶⁵⁸⁶³ is an apocalyptic number.

665863 is a deficient number, since it is larger than the sum of its proper divisors (66169).

665863 is a wasteful number, since it uses less digits than its factorization.

665863 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5525 (or 5514 counting only the distinct ones).

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

The square root of 665863 is about 816.0042892044. The cubic root of 665863 is about 87.3229289835.

It can be divided in two parts, 66 and 5863, that added together give a square (5929 = 77²).

The spelling of 665863 in words is "six hundred sixty-five thousand, eight hundred sixty-three".