8205136820521 has 27 divisors (see below), whose sum is σ = 8416854115383. Its totient is φ = 7998720896400.

The previous prime is 8205136820497. The next prime is 8205136820633. The reversal of 8205136820521 is 1250286315028.

The square root of 8205136820521 is 2864461.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 7883398292121 + 321738528400 = 2807739^2 + 567220^2 .

It is not a de Polignac number, because 8205136820521 - 2⁹ = 8205136820009 is a prime.

It is a super-2 number, since 2×8205136820521² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8205136830521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 22855534140 + ... + 22855534498.

Almost surely, 2^{8205136820521} is an apocalyptic number.

8205136820521 is the 2864461-st square number.

8205136820521 is the 1432231-st centered octagonal number.

It is an amenable number.

8205136820521 is a deficient number, since it is larger than the sum of its proper divisors (211717294862).

8205136820521 is an frugal number, since it uses more digits than its factorization.

8205136820521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1078 (or 539 counting only the distinct ones).

The product of its (nonzero) digits is 230400, while the sum is 43.

The spelling of 8205136820521 in words is "eight trillion, two hundred five billion, one hundred thirty-six million, eight hundred twenty thousand, five hundred twenty-one".