815661 has 36 divisors (see below), whose sum is σ = 1493856. Its totient is φ = 419760.

The previous prime is 815653. The next prime is 815663. The reversal of 815661 is 166518.

815661 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 815661 - 2³ = 815653 is a prime.

It is a congruent number.

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 in 35 ways as a sum of consecutive naturals, for example, 7570 + ... + 7676.

It is an arithmetic number, because the mean of its divisors is an integer number (41496).

2⁸¹⁵⁶⁶¹ is an apocalyptic number.

It is an amenable number.

815661 is a deficient number, since it is larger than the sum of its proper divisors (678195).

815661 is a wasteful number, since it uses less digits than its factorization.

815661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142 (or 128 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 815661 is about 903.1395241047. The cubic root of 815661 is about 93.4336322564.

The spelling of 815661 in words is "eight hundred fifteen thousand, six hundred sixty-one".