665815 has 16 divisors (see below), whose sum is σ = 848160. Its totient is φ = 501120.

The previous prime is 665813. The next prime is 665843. The reversal of 665815 is 518566.

665815 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 665815 - 2¹ = 665813 is a prime.

It is a super-2 number, since 2×665815² = 886619228450, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665813) 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, 10885 + ... + 10945.

It is an arithmetic number, because the mean of its divisors is an integer number (53010).

2⁶⁶⁵⁸¹⁵ is an apocalyptic number.

665815 is a deficient number, since it is larger than the sum of its proper divisors (182345).

665815 is a wasteful number, since it uses less digits than its factorization.

665815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162.

The product of its digits is 7200, while the sum is 31.

The square root of 665815 is about 815.9748770642. The cubic root of 665815 is about 87.3208306533.

The spelling of 665815 in words is "six hundred sixty-five thousand, eight hundred fifteen".