812256721 has 4 divisors (see below), whose sum is σ = 812600244. Its totient is φ = 811913200.

The previous prime is 812256703. The next prime is 812256733. The reversal of 812256721 is 127652218.

It is a happy number.

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 171610000 + 640646721 = 13100^2 + 25311^2 .

It is a cyclic number.

It is not a de Polignac number, because 812256721 - 2¹⁵ = 812223953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (812256791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 168190 + ... + 172951.

It is an arithmetic number, because the mean of its divisors is an integer number (203150061).

Almost surely, 2^812256721 is an apocalyptic number.

It is an amenable number.

812256721 is a deficient number, since it is larger than the sum of its proper divisors (343523).

812256721 is a wasteful number, since it uses less digits than its factorization.

812256721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343522.

The product of its digits is 13440, while the sum is 34.

The square root of 812256721 is about 28500.1179120368. The cubic root of 812256721 is about 933.0346474376.

The spelling of 812256721 in words is "eight hundred twelve million, two hundred fifty-six thousand, seven hundred twenty-one".