816681 has 4 divisors (see below), whose sum is σ = 1088912. Its totient is φ = 544452.

The previous prime is 816667. The next prime is 816689. The reversal of 816681 is 186618.

816681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 816681 - 2⁵ = 816649 is a prime.

It is a super-2 number, since 2×816681² = 1333935711522, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (816689) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136111 + ... + 136116.

It is an arithmetic number, because the mean of its divisors is an integer number (272228).

2⁸¹⁶⁶⁸¹ is an apocalyptic number.

It is an amenable number.

816681 is a deficient number, since it is larger than the sum of its proper divisors (272231).

816681 is a wasteful number, since it uses less digits than its factorization.

816681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 272230.

The product of its digits is 2304, while the sum is 30.

The square root of 816681 is about 903.7040444747. The cubic root of 816681 is about 93.4725628933.

The spelling of 816681 in words is "eight hundred sixteen thousand, six hundred eighty-one".