809971681 has 4 divisors (see below), whose sum is σ = 857617092. Its totient is φ = 762326272.

The previous prime is 809971667. The next prime is 809971733. The reversal of 809971681 is 186179908.

809971681 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.

It can be written as a sum of positive squares in 2 ways, for example, as 630813456 + 179158225 = 25116^2 + 13385^2 .

It is a cyclic number.

It is not a de Polignac number, because 809971681 - 2¹³ = 809963489 is a prime.

It is a super-2 number, since 2×809971681² = 1312108248043931522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (809971651) 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, 23822680 + ... + 23822713.

It is an arithmetic number, because the mean of its divisors is an integer number (214404273).

Almost surely, 2^809971681 is an apocalyptic number.

It is an amenable number.

809971681 is a deficient number, since it is larger than the sum of its proper divisors (47645411).

809971681 is a wasteful number, since it uses less digits than its factorization.

809971681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47645410.

The product of its (nonzero) digits is 217728, while the sum is 49.

The square root of 809971681 is about 28460.0014230499. The cubic root of 809971681 is about 932.1588882377.

It can be divided in two parts, 8099716 and 81, that multiplied together give a square (656076996 = 25614²).

The spelling of 809971681 in words is "eight hundred nine million, nine hundred seventy-one thousand, six hundred eighty-one".