6561521539 has 4 divisors (see below), whose sum is σ = 6561816480. Its totient is φ = 6561226600.

The previous prime is 6561521537. The next prime is 6561521557. The reversal of 6561521539 is 9351251656.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6561521539 - 2¹ = 6561521537 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 6561521495 and 6561521504.

It is not an unprimeable number, because it can be changed into a prime (6561521537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111112 + ... + 159589.

It is an arithmetic number, because the mean of its divisors is an integer number (1640454120).

Almost surely, 2^6561521539 is an apocalyptic number.

6561521539 is a deficient number, since it is larger than the sum of its proper divisors (294941).

6561521539 is a wasteful number, since it uses less digits than its factorization.

6561521539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294940.

The product of its digits is 243000, while the sum is 43.

The square root of 6561521539 is about 81003.2193125681. The cubic root of 6561521539 is about 1872.1250436774.

The spelling of 6561521539 in words is "six billion, five hundred sixty-one million, five hundred twenty-one thousand, five hundred thirty-nine".