6545581821 has 6 divisors (see below), whose sum is σ = 9454729310. Its totient is φ = 4363721208.

The previous prime is 6545581787. The next prime is 6545581843. The reversal of 6545581821 is 1281855456.

6545581821 is a `hidden beast` number, since 6 + 5 + 45 + 581 + 8 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 4232933721 + 2312648100 = 65061^2 + 48090^2 .

It is not a de Polignac number, because 6545581821 - 2⁹ = 6545581309 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 (6545586821) 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, 363643426 + ... + 363643443.

Almost surely, 2^6545581821 is an apocalyptic number.

It is an amenable number.

6545581821 is a deficient number, since it is larger than the sum of its proper divisors (2909147489).

6545581821 is a wasteful number, since it uses less digits than its factorization.

6545581821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 727286875 (or 727286872 counting only the distinct ones).

The product of its digits is 384000, while the sum is 45.

The square root of 6545581821 is about 80904.7700756884. The cubic root of 6545581821 is about 1870.6078477127.

The spelling of 6545581821 in words is "six billion, five hundred forty-five million, five hundred eighty-one thousand, eight hundred twenty-one".