812808721 has 4 divisors (see below), whose sum is σ = 826585200. Its totient is φ = 799032244.

The previous prime is 812808697. The next prime is 812808739. The reversal of 812808721 is 127808218.

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, and also an emirpimes, since its reverse is a distinct semiprime: 127808218 = 2 ⋅63904109.

It is a cyclic number.

It is not a de Polignac number, because 812808721 - 2⁷ = 812808593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (812808751) 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, 6888151 + ... + 6888268.

It is an arithmetic number, because the mean of its divisors is an integer number (206646300).

Almost surely, 2^812808721 is an apocalyptic number.

It is an amenable number.

812808721 is a deficient number, since it is larger than the sum of its proper divisors (13776479).

812808721 is a wasteful number, since it uses less digits than its factorization.

812808721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13776478.

The product of its (nonzero) digits is 14336, while the sum is 37.

The square root of 812808721 is about 28509.8004377442. The cubic root of 812808721 is about 933.2459593236.

The spelling of 812808721 in words is "eight hundred twelve million, eight hundred eight thousand, seven hundred twenty-one".