812721 has 24 divisors (see below), whose sum is σ = 1346880. Its totient is φ = 426816.

The previous prime is 812717. The next prime is 812731. The reversal of 812721 is 127218.

812721 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 812721 - 2² = 812717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an alternating number because its digits alternate between even and odd.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 812721.

It is not an unprimeable number, because it can be changed into a prime (812701) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3435 + ... + 3663.

It is an arithmetic number, because the mean of its divisors is an integer number (56120).

2⁸¹²⁷²¹ is an apocalyptic number.

It is an amenable number.

812721 is a deficient number, since it is larger than the sum of its proper divisors (534159).

812721 is a wasteful number, since it uses less digits than its factorization.

812721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265 (or 252 counting only the distinct ones).

The product of its digits is 224, while the sum is 21.

The square root of 812721 is about 901.5103992745. The cubic root of 812721 is about 93.3212385121.

Adding to 812721 its reverse (127218), we get a palindrome (939939).

The spelling of 812721 in words is "eight hundred twelve thousand, seven hundred twenty-one".