813797721 has 72 divisors (see below), whose sum is σ = 1398138560. Its totient is φ = 454196160.

The previous prime is 813797717. The next prime is 813797729. The reversal of 813797721 is 127797318.

It is not a de Polignac number, because 813797721 - 2² = 813797717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (813797729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 765036 + ... + 766098.

Almost surely, 2^813797721 is an apocalyptic number.

It is an amenable number.

813797721 is a deficient number, since it is larger than the sum of its proper divisors (584340839).

813797721 is a wasteful number, since it uses less digits than its factorization.

813797721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1147 (or 1133 counting only the distinct ones).

The product of its digits is 148176, while the sum is 45.

The square root of 813797721 is about 28527.1400774771. The cubic root of 813797721 is about 933.6243206492.

The spelling of 813797721 in words is "eight hundred thirteen million, seven hundred ninety-seven thousand, seven hundred twenty-one".