815666 has 4 divisors (see below), whose sum is σ = 1223502. Its totient is φ = 407832.

The previous prime is 815663. The next prime is 815669. The reversal of 815666 is 666518.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (815663) and next prime (815669).

It can be written as a sum of positive squares in only one way, i.e., 801025 + 14641 = 895^2 + 121^2 .

It is a super-2 number, since 2×815666² = 1330622047112, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (815663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 203915 + ... + 203918.

2⁸¹⁵⁶⁶⁶ is an apocalyptic number.

815666 is a deficient number, since it is larger than the sum of its proper divisors (407836).

815666 is a wasteful number, since it uses less digits than its factorization.

815666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 407835.

The product of its digits is 8640, while the sum is 32.

The square root of 815666 is about 903.1422922220. The cubic root of 815666 is about 93.4338231720.

The spelling of 815666 in words is "eight hundred fifteen thousand, six hundred sixty-six".