6561697219561 has 9 divisors (see below), whose sum is σ = 7212475023229. Its totient is φ = 5965153674700.

The previous prime is 6561697219547. The next prime is 6561697219669. The reversal of 6561697219561 is 1659127961656.

The square root of 6561697219561 is 2561581.

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

It is not a de Polignac number, because 6561697219561 - 2⁷ = 6561697219433 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 6561697219493 and 6561697219502.

It is not an unprimeable number, because it can be changed into a prime (6561697219261) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 28060956 + ... + 28293826.

Almost surely, 2^{6561697219561} is an apocalyptic number.

6561697219561 is the 2561581-st square number.

6561697219561 is the 1280791-st centered octagonal number.

It is an amenable number.

6561697219561 is a deficient number, since it is larger than the sum of its proper divisors (650777803668).

6561697219561 is an frugal number, since it uses more digits than its factorization.

6561697219561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 465764 (or 232882 counting only the distinct ones).

The product of its digits is 36741600, while the sum is 64.

Multiplying 6561697219561 by its sum of digits (64), we get a square (419948622051904 = 20492648²).

The spelling of 6561697219561 in words is "six trillion, five hundred sixty-one billion, six hundred ninety-seven million, two hundred nineteen thousand, five hundred sixty-one".