820644135525 has 36 divisors (see below), whose sum is σ = 1472247355332. Its totient is φ = 436967435520.

The previous prime is 820644135433. The next prime is 820644135527. The reversal of 820644135525 is 525531446028.

820644135525 is a `hidden beast` number, since 8 + 20 + 64 + 4 + 13 + 552 + 5 = 666.

820644135525 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 6 ways, for example, as 144437242401 + 676206893124 = 380049^2 + 822318^2 .

It is not a de Polignac number, because 820644135525 - 2⁹ = 820644135013 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820644135527) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 2816854 + ... + 3094503.

Almost surely, 2^820644135525 is an apocalyptic number.

It is an amenable number.

820644135525 is a deficient number, since it is larger than the sum of its proper divisors (651603219807).

820644135525 is a wasteful number, since it uses less digits than its factorization.

820644135525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5911990 (or 5911982 counting only the distinct ones).

The product of its (nonzero) digits is 1152000, while the sum is 45.

The spelling of 820644135525 in words is "eight hundred twenty billion, six hundred forty-four million, one hundred thirty-five thousand, five hundred twenty-five".