812563821 has 6 divisors (see below), whose sum is σ = 1173703310. Its totient is φ = 541709208.

The previous prime is 812563813. The next prime is 812563867. The reversal of 812563821 is 128365218.

It is a happy number.

812563821 is a `hidden beast` number, since 8 + 12 + 5 + 638 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 610781796 + 201782025 = 24714^2 + 14205^2 .

It is not a de Polignac number, because 812563821 - 2³ = 812563813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (812563811) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 45142426 + ... + 45142443.

Almost surely, 2^812563821 is an apocalyptic number.

It is an amenable number.

812563821 is a deficient number, since it is larger than the sum of its proper divisors (361139489).

812563821 is a wasteful number, since it uses less digits than its factorization.

812563821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90284875 (or 90284872 counting only the distinct ones).

The product of its digits is 23040, while the sum is 36.

The square root of 812563821 is about 28505.5050998925. The cubic root of 812563821 is about 933.1522206256.

The spelling of 812563821 in words is "eight hundred twelve million, five hundred sixty-three thousand, eight hundred twenty-one".