666815 has 8 divisors (see below), whose sum is σ = 805488. Its totient is φ = 529920.

The previous prime is 666811. The next prime is 666821. The reversal of 666815 is 518666.

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

It is not a de Polignac number, because 666815 - 2² = 666811 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 (666811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 620 + ... + 1310.

It is an arithmetic number, because the mean of its divisors is an integer number (100686).

2⁶⁶⁶⁸¹⁵ is an apocalyptic number.

666815 is a deficient number, since it is larger than the sum of its proper divisors (138673).

666815 is a wasteful number, since it uses less digits than its factorization.

666815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 889.

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

The square root of 666815 is about 816.5874111202. The cubic root of 666815 is about 87.3645250483.

The spelling of 666815 in words is "six hundred sixty-six thousand, eight hundred fifteen".