817681 has 4 divisors (see below), whose sum is σ = 831600. Its totient is φ = 803764.

The previous prime is 817679. The next prime is 817697. The reversal of 817681 is 186718.

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 a cyclic number.

It is not a de Polignac number, because 817681 - 2¹ = 817679 is a prime.

It is a super-2 number, since 2×817681² = 1337204435522, which contains 22 as substring.

It is a Duffinian number.

817681 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (817651) 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, 6871 + ... + 6988.

It is an arithmetic number, because the mean of its divisors is an integer number (207900).

2⁸¹⁷⁶⁸¹ is an apocalyptic number.

It is an amenable number.

817681 is a deficient number, since it is larger than the sum of its proper divisors (13919).

817681 is a wasteful number, since it uses less digits than its factorization.

817681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13918.

The product of its digits is 2688, while the sum is 31.

The square root of 817681 is about 904.2571536903. The cubic root of 817681 is about 93.5106987290.

It can be divided in two parts, 8 and 17681, that added together give a square (17689 = 133²).

The spelling of 817681 in words is "eight hundred seventeen thousand, six hundred eighty-one".